Those of you who regularly read our baseball blogging probably know we have a mild fascination with WPA, Win Probability Added. If you’re not familiar, the purpose of WPA is to measure how a game’s win probability shifts with every play and to then credit that shift to the batter and the pitcher. If each team has a 50% chance to win the game before a batter strikes out, and if the batter’s team’s win probability is 48% after the strikeout, then the pitcher receives credit for +0.02 WPA and the batter receives credit for –0.02 WPA. I personally consider WPA an elegant way of breaking a single game down into the sum of its moments, a fascinating and fairly effective method of identifying who, exactly, made wins happen.
WPA does have its limitations, though, and as with a lot of stats, most of those come when the ball is in the field of play. Let’s take three examples, all from the Twins–Blue Jays series:
In Game 1 of the series, on Tuesday, Bo Bichette was scrambling to score from second base in the fourth inning after a Kevin Kiermaier groundball dribbled softly beneath third baseman Jorge Polanco’s glove. There’s a good chance you saw the play. Carlos Correa, standing near second base, noticed the situation developing and managed to race over, pick up the ball, and fire an accurate throw home to catcher Ryan Jeffers, who managed to apply the tag in time. It was a complex moment, one of the highest-leverage plays of the game, and those who decided the outcome—Polanco, who failed to field the ball cleanly; Correa, who topped the baseline duty of paying attention with a tremendously skilled play to get the ball to Jeffers; Jeffers, who fielded the throw and applied the tag on time without violating the plate-blocking rule; and Bichette, who if memory serves briefly pulled up as he rounded third base, presumably fearing Polanco would field the ball cleanly but not throw to first, in which case it would have been wisest for Bichette to wait at third base. Polanco affected the Twins’ win probability negatively. Correa and Jeffers each affected it positively. Bichette’s performance was debatable. On the WPA ledger? None of the four are even recognized. WPA—at least the FanGraphs version, which we use—saw runners on first and second base with two outs and then saw an inning over. The Twins’ win probability increased by four percentage points. –0.04 WPA for the batter, Kevin Kiermaier. +0.04 WPA for the pitcher, Pablo López. WPA views complicated plays simply, and in doing so, it fails to grasp some of the biggest contributions in a given game.
In Game 2 of the series, yesterday, Vladimir Guerrero Jr. was picked off second base. Bichette was at the plate, the Blue Jays were threatening to score, and Sonny Gray threw behind Guerrero to Correa, who tagged Guerrero out, extinguishing the threat. The win probability? It shifted by eight percentage points in the Twins’ favor, and WPA does have such capacity that it was able to assign –0.08 WPA to Guerrero, but Correa made a good play again, deserving at least some of the credit. All +0.08 WPA went to Gray. WPA can handle baserunners, but again it fails to distribute credit across fielders, deferring to the pitcher.
Later in Game 2, Matt Chapman hit a line drive down the left field line which looked poised to tie the game. The bases were loaded, there was one out, and Chapman’s line drive was a no-doubt double, one which would have at least tied the game and potentially given the Blue Jays the lead if it stayed in the field of play rather than bouncing into the stands and holding the runner at third. Instead, it landed inches foul, and Chapman went on to hit into a double play. WPA took no look at the foul ball. WPA, like so many small-sample stats in baseball, does not account for luck.
These are major limitations. WPA does not fully accomplish what it sets out to do. In a perfect world, WPA would be the end result of the bWAR approach, measuring the actual impact of each player on every game. But there is too much luck, and there are other external factors, and the competition is not truly a binary one between hitter and pitcher. I wouldn’t be surprised if future iterations of WPA make greater strides towards this aim, including adjustments for the non-linear nature of probability (the gap between 90% and 100% is different from the gap between 50% and 60%). As it stands, it’s useful enough to use, but in this small a sample, we’re going to have to make judgment calls. Here’s who won each team each series this week, with some help from WPA:
Twins over Blue Jays
The winners:
- Sonny Gray
- Royce Lewis
- Caleb Thielbar
- Pablo López
- Carlos Correa
- Rocco Baldelli et al.
The Twins got two very, very good starts. This was a theme in three of the four series, and it hearkens back to when we used to have a Wild Card Game. In one single game, rarely is a single player more important than a starting pitcher. Over the course of a season, the best bat is almost always more valuable than the best arm, but in a single game, a pitcher makes a huge difference, and at the onset of a postseason, pitchers are set up better to make the performances in question, coming off normal rest. López worked into the sixth inning on Tuesday, allowing just the one run. Gray worked five scoreless yesterday. Gray’s was the more impressive outing by all controllable metrics—he struck more Blue Jays out and limited the hard-hit balls more thoroughly than López—but despite it not being López’s best outing, his was similarly excellent in its impact. An argument can even be made that López’s success helped force the Blue Jays into bullpen aggression which ultimately did not serve them well, though most of that was their gameplan yesterday, which failed to account for the scenario in which José Berríos was pitching even better than Gray or López did.
Out of the bullpen, Caleb Thielbar deserves credit, following up a clean inning on Tuesday with a necessary escape yesterday. It was Thielbar on the mound when Chapman’s would’ve–been–double landed foul. It was Thielbar who induced the double play ball in the aftermath. Was Thielbar lucky the ball landed foul? Yes. But Thielbar would have been unlucky had the ball nicked the foul line. Thielbar allowed luck into the equation, or Chapman forced luck into it, but the end result was that after the luck had its say, Thielbar got the outs.
For this, Rocco Baldelli and whoever else was making the Twins’ pitching decisions deserves credit. As with all of this, there’s no counterfactual, and sometimes a great managerial move ends up like a 110-mph line drive double play. But the point of this WPA focus is to not worry too much about who played the best or managed the smartest. The point is to look at how everything worked out. Over the long haul, you want to look at the quality of everything and not only the results. In the short term, we only have results. We are not saying Thielbar pitched excellently or Baldelli managed excellently: We’re saying the things they tried worked out. Baldelli pulled what turned out to be the right levers at the right time.
We’ve made it this far without mentioning Royce Lewis, and that is a wild thing, given what Royce Lewis did on Tuesday, coming off a two-week stay on the injured list to homer in his first career postseason at-bat, giving the Twins a 2–0 lead they would keep. Two innings later? He did it again, providing the insurance himself. Royce Lewis is always going to be a folk hero in the Twins Cities. Royce Lewis is always going to receive the most credit for ending a postseason losing streak which lasted roughly 19 years. That is good and fair.
You can’t tell the story of these two games, though, without mentioning Correa, who like Lewis had been nursing an injury and like Lewis showed up in big ways. Correa was a limited factor at the plate—he drove in an important run yesterday, but he left others on the table—but he showed up in the field, with the play to throw Bichette out at home accented by the pickoff, in which he not only caught Gray’s pickoff throw and successfully applied the tag, but also found his way to the bag without attracting Guerrero’s notice. There were other important defensive efforts—Michael A. Taylor made a nice catch on another hard-hit Chapman ball (find me an unluckier man these last two years than Matt Chapman)—but Correa made two of them at the most crucial times. The Twins may go on to rue his contract, and the numbers won’t tell this piece of the story, but Carlos Correa kept the Blue Jays from getting back in this series after Royce Lewis knocked them out of it in its first inning.
Rangers over Rays
The winners:
- Jordan Montgomery
- Corey Seager
- Evan Carter
- Nathan Eovaldi
We talked a lot above about how pitchers get credit for their defense in this WPA dichotomy. That does work, however, when it’s the pitcher himself who is making the play.
In the second inning on Tuesday, Jordan Montgomery had yet to strike out a batter, having allowed three soft singles to the first seven hitters he’d faced. Texas had taken a 1–0 lead in the top half of the second, but the Rays were threatening when Jose Siri popped up a bunt towards the first base line and Montgomery sent his giant frame airborne after it. Montgomery came down with the ball in his glove. Had Montgomery not caught it, the ball may have gone foul, but again—the result is what counts. Montgomery retired Siri, punished the Rays for trying to bunt on him, and grabbed himself a neat +0.08 on the WPA ledger on his way to a +0.35 total, among the best of the entire week. After the catch, it got even better, Montgomery striking out five without walking a batter, limiting the Rays’ contact while Siri, Tyler Glasnow, and the defense cracked under the pressure. Jordan Montgomery was not the MVP of the week, but he was the most valuable guy on the AL side.
At the plate, Corey Seager did a lot. The AL MVP candidate played like an AL MVP candidate, reaching base six times in ten tries with a trio of doubles hit between 103 and 109 mph. His leadoff double in the fifth on Tuesday set the Rangers up to extend their lead on the Glasnow wild pitch. His single in the sixth set Siri up to throw the ball away in a play that turned out to be the dagger. Seager didn’t hit a dramatic home run or lead any sensational comeback. But he made the Rays deal with him, and they couldn’t do that.
Rookie Evan Carter—not even a rookie, technically, if my understanding of his 2024 rookie status is correct given how late in the year he was called up to the majors—had the biggest single hit of the two games, his two-run homer in the fourth inning yesterday turning a tight game into the beginnings of a blowout. He didn’t make a single out on Tuesday, either. If you combine a lot of conventional wisdom—which is about the furthest thing from the scientific process but can be interesting, as we’ll hopefully show—you can make a claim that Rays fans so sparsely attending the two games removed some of the pressure from what should have been the highest-pressure moments, moments which have made players both experienced and inexperienced wilt throughout the years.
Lastly, pitching better than Montgomery but with more of a cushion, Nathan Eovaldi kept the Rays from ever getting much hope in Game 2. He didn’t finish his final inning, which can have some effects on how momentum is remembered, but his eight strikeouts without a walk maintained the tone Montgomery set. It was an impactful performance, but the biggest thing it did was establish a ton of confidence in Eovaldi after his average box score line in six post-injury starts went something like: 3.1 IP, 4 ER, 1 HR, 2 BB, 4 K. This was a lot better, and it came against an offense that even without Wander Franco should have been one of the better ones in the league.
Phillies over Marlins
The winners:
- Aaron Nola
- Zack Wheeler
- Trea Turner
- José Alvarado
The Marlins’ formula for winning this series was to either get unexpected gems from their starting pitchers or to induce chaos. The Phillies stymied both these efforts. And while the bats performed—eleven runs over two games is a lot—they didn’t fully need to. Bryson Stott’s grand slam made a difference, but not in the outcome of the game so much as in when that outcome was decided. So, Trea Turner makes his appearance on this list—in part due to a first inning double on Tuesday that was key when he hit it but merely set up a disappointing Bryce Harper strikeout—but this is about the pitchers.
Jordan Montgomery may have had the most consequential outing of the two days, but Zack Wheeler tied with Eovaldi for the best. Each recorded twenty outs. Each struck out eight batters. Neither walked a batter or allowed a home run. Eovaldi faced one more guy, so Wheeler was a little more efficient, but they were both so dominant, and each did exactly what their offense needed them to do: They squelched any hope the other team might have once they fell behind.
For the most part, that is.
Wheeler needed some help, and José Alvarado provided it, striking out Yuli Gurriel with the tying runner on base after Wheeler exited on Tuesday, shutting down the one opportunity the Marlins produced to make some serious noise. Bullpen guys shine big in October (we’re about to see a lot of that, by the way) and while Alvarado’s outing wasn’t the biggest one we’ll see this postseason, it was the biggest of this series.
Aaron Nola did his best Zack Wheeler impression last night, and while it wasn’t Wheeler (Walking a batter? Come on, man), it was again good enough for the Phillies’ purposes. One underappreciated thing about it? Nola never let the Marlins have a meaningful scoring chance. Wheeler left with the outcome a little bit in doubt. Nola kept the door closed until Stott’s grand slam was in the seats and the party was on.
Diamondbacks over Marlins
The winners:
- Corbin Carroll
- Andrew Saalfrank
- Evan Longoria & Ryan Thompson
- Torey Lovullo et al.
There was a lot of leverage in these two games.
What we mean by that is that because of the nature of the games’ respective scripts—tense, dramatic contests with a comeback each and competitive moments late into the evening—more plays were worth more than they were in the other three series. There were more crucial moments, and the way this worked out was that guys who showed up big in one moment also let the situation down in another: Tyrone Taylor hit a huge home run for the Brewers in Game 1, but later in Game 1 he left runners in scoring position twice.
On the aggregate, this only worked out in a largely positive manner for one or two Diamondbacks hitters. Among them? As could have been predicted, Corbin Carroll. The presumptive NL Rookie of the Year and MVP vote-getter hit the home run on Tuesday which reintroduced Arizona to the game, one in which they’d looked dead to rights moments earlier, trailing by three against one of the best pitchers in the sport. He also:
- Drew the walk which forced Burnes from the game in the fifth inning.
- Led off the seventh inning with a single.
- Drew the walk which sparked the ninth inning rally.
- Got caught stealing by a catcher not known for stopping the running game.
And that was just Game 1! Carroll’s double off of Freddy Peralta helped chase the Brewers’ de facto second starter in Game 2, setting Ketel Marte up for the single which finished Peralta off and gave Arizona its ultimate lead. The Diamondbacks scored in four of their 18 innings at bat in this series. Carroll reached base in three of those innings.
As was said, the series was not without drama. Kevin Ginkel was a hero on Tuesday. On Wednesday? Nearly a goat. Andrew Saalfrank came in and saved the day, though, inducing a Sal Frelick tapper and a Willy Adames groundout after the Brewers put the tying run on base in the eighth inning. Saalfrank was not at the top of Torey Lovullo’s list of bullpen arms (this was part of why Ginkel was out there again after throwing a lot of high-pressure pitches in Game 1), but he ended up being the second-most valuable player of the series, at least by our adjusted read based on WPA.
We have another situation here where one gigantic defensive play swung a game, and in this case, it was Ryan Thompson pitching and Evan Longoria recording the outs. The Brewers had briefly become the live favorites in the fifth inning of Game 1 before Thompson entered, and it looked off the bat like Tyrone Taylor had singled, something which would have almost certainly scored two runs. In fact, it looked so much like this that the Diamondbacks’ play-by-play man on the radio feed (apologies for not knowing which was calling it at that time) said it was a base hit before excitedly correcting himself. I wish I knew how to access to the Statcast data on that specific play, just to have some perspective on how unlikely the catch was, but the swing between that ball reaching the outfield grass and that ball landing in Longoria’s glove had to be somewhere close to 50 percentage points. Credit to Thompson for the pitch, but what a catch by Longoria. The Brewers were going to have two runners on and still one out while leading by one. Instead, the Diamondbacks exited the fifth inning with the lead intact.
One measure of how easy or difficult a series was is how many uniformed players took the field for the victors. The Rangers? Only 14 guys. The Diamondbacks? 20. Torey Lovullo had to use 20 players, including his backup catcher thanks to Gabriel Moreno getting hit on the head by a follow-through. As with Baldelli, we don’t know whether Lovullo made the right moves, but as with all of this: They worked out.
**
We’ll have more thoughts tomorrow on the Division Series matchups, but it’s worth a quick mention of how big it is to sweep these three-game series rather than letting them go the distance. Relievers pitch on three consecutive days so rarely that to expect one to do that and then turn around and pitch a fourth time in five days is a lot. Hitters have bumps and bruises galore at this point in the calendar. And as Moreno’s injury showed, the more innings of baseball you play, the more that can go wrong. That’s without getting into what it does for each of these teams’ Game 1 starting pitching situations on Saturday. It isn’t as much fun as getting ourselves single-elimination games tonight, but the added rest should make all four matchups closer in the next round. Buckle up.
