I love the metric Win Probability Added (WPA). It’s “the story stat”, a way to quantify the contributions made by players in a single game or across an entire season. Basically it measures an player’s contribution (positive or negative) to his team’s chances of winning a game. You measure it by calculating his team’s chance to win the game before his plate appearance and after it, and subtracting the former from the latter. You can do this for both batters and pitchers; a positive WPA event for a batter brings a corresponding negative WPA for the pitcher he’s facing, and vice versa.

So a WPA of .635 means that player, overall, increased his team’s chance of winning by 63.5%. When you add up a player’s WPA across an entire season or career, you can get an idea of how important that player was to his team(s). It’s not the end-all-be-all measure of value (for several reasons I won’t go into here), but it’s useful in telling exciting stories because it usually involves a sudden reversal-of-fortune.

The following list is the five games this year where an AL batter contributed the most to his team’s chance of winning the game, followed by the five pitchers with the biggest single-game contributions to their teams. Note that WPA is cumulative, meaning if a player had five plate appearances in a game, he got five chances to contribute (or take away from) to his team’s chance to win. So it’s not fair to compare players who have a different number of PA in a game (or over a season), but I’m not doing that. I’m just describing games where a player truly carried his team to victory.

Batters

5. Torii Hunter vs. Oakland A’s, August 29th

Hunter entered the game as pinch hitter in the bottom of the 7th with two outs, runners on first and second, and the Tigers behind 6-3. Jim Leyland must’ve wanted to get something going, but Hunter grounded out.

When Hunter came up again, it was the bottom of the 9th and the Tigers were facing the A’s closer Grant Balfour, same score. Balfour struggled a bit, walking Austin Jackson to start the inning before getting Andy Dirks to pop out and Alex Avila to strike out. With two outs, Jackson moved up to second on defensive indifference. Prince Fielder walked, and Victor Martinez singled to bring home Jackson.

With the score now 6-4 and two on with two out, Hunter stepped to the plate. The Tigers had only a 10% chance of winning this game. He fouled off a backdoor slider for strike one, then took a 94 MPH heater high for ball one. Balfour returned to the backdoor slider but elevated it. Hunter pulled it over the left-center fence for a three-run walkoff homer.

Hunter’s WPA for the game: 0.850.

4. Jason Giambi vs. Chicago White Sox, September 24th

Addison Reed, the White Sox closer, took the mound in the bottom of the ninth inning with his team ahead 4-3. This game meant nothing to the White Sox, who were already eliminated from postseason play, but the Indians were fighting for a wild card berth and Reed had a chance to play spoiler. He struck out Yan Gomes to start the inning but gave up a single to Michael Brantley. Mike Aviles came up next and struck out. Up next came Jason Giambi, elder statesman but still a dangerous hitter, to pinch hit. The Indians had a 13% chance to win the game.

The first pitch was a slider almost in the dirt that Giambi whiffed on for strike one. The second pitch was a heater that missed low and inside for ball one; Brantley stole second on pitch. The third pitch was a well-placed slider, juuuuust barely in the strike zone at the lower-inside corner. It was an excellent pitch, but Giambi got a hold of it for a two-run homer, giving the Indians a dramatic 5-4 win and keeping their postseason hopes alive.

Giambi’s WPA for the game: 0.865.

3. Evan Longoria vs. San Diego Padres, May 11th

Unlike Hunter and Giambi, Longoria played the whole game instead of just a couple of plate appearances. He walked in his first plate appearance and scored when James Loney hit a home run. The Rays batted around that inning, scoring six runs, but couldn’t hold the lead, giving up seven to the Padres during the course of the game.

In the bottom of the 9th, Huston Street came on to close a 7-6 win for the Padres. He immediately got two flyball outs from Matt Joyce and Kelly Johnson, putting the Rays in a deep hole. But Ben Zobrist worked a seven-pitch walk to keep the Rays’ hopes alive.

Up stepped Longoria with the Rays having a piddling 9% chance to win the game  Street threw him a sinker that missed way outside for ball one, then a backdoor slider that Longoria chased for strike one. Street missed with a second slider for ball two, then threw the pitch he’d regret the most, a hanging slider that Longoria crushed for a two-run walkoff homer. Ballgame.

Longoria’s WPA for the game: 0.877.

2. Munenori Kawasaki vs. Baltimore Orioles, May 26th

As an O’s fan, this one hurts to write about, but Kawasaki crushed us in this game. He had two big hits. The first came in the 8th inning; with the Jays behind 3-1, Tommy Hunter gave up a single to J.P. Arencibia and hit Brett Lawrie with a pitch, putting a runner in scoring position. Hunter struck out Anthony Gose but walked Colby Rasmus to load the bases. Kawasaki took his turn, looked at ball one, and singled to center field to drive in Arencibia.

It was now a 3-2 game, but the O’s scored two in the top of the 9th to make it 5-2. In came Jim Johnson, who was so good for the O’s in 2012, to face the Jays 3-4-5 batters. He wouldn’t make it out of the inning. Edwin Encarnacion doubled and Adam Lind singled, putting runners on the corners for Arencibia, who singled to drive in Encarnacion. 5-3 O’s, and Lind moved to third. Lawrie flew out but Gose walked, pushing Arencibia to second base with Lind still on third. Mark DeRosa grounded into a force play at second, scoring Lind to make it a one-run game.

With two outs, two on, and the O’s clinging to a one-run lead, Kawasaki came up again. Even though there were two outs, the Jays had a 20% chance to win the game because two runners were on base. Pitch one was a sinker low for ball one, followed by another sinker low for ball two. A third sinker up and away got strike one, another sinker missed high for ball three, and a fifth sinker came in for called strike two. Full count, and Kawasaki hadn’t even swung.

The sixth pitch came in, another sinker, this one at 95 MPH, and it crossed the middle of the plate about thigh high. Kawasaki drove it to left-center for a double, scoring both runners easily and winning the game 6-5.

Kawasaki’s WPA for the game: 0.954.

1. Jose Bautista vs. Tampa Bay Rays, May 22nd

But Kawasaki was merely following in the footsteps of his teammate Jose Bautista, who’d almost single-handedly destroyed the Rays four days earlier. He got started early, driving in Anthony Gose in the bottom of the first inning to kick off the game’s scoring. He may have had a shot to score himself, but he was doubled off at second base on a flyout. He made up for it later in the bottom of the fourth, when he homered to tie the game at 2. Later, in the sixth, he walked.

Fast forward to the bottom of the 9th. The Jays hadn’t scored since Bautista’s home run and were behind 3-2, facing the Rays closer Fernando Rodney. Who led off the inning? None other than Jose Bautista, who worked the count full before blasting his second home run of the game. That tied the score at 3, but the Jays couldn’t score again in the inning, moving things along to the 10th.

The Rays went 1-2-3 against Aaron Loup, but Cesar Ramos didn’t have such luck in the bottom half. Colby Rasmus singled to start the inning, and Emilio Bonifacio sacrificed him to second base. Our pal Kawasaki then grounded out, advancing Rasmus to third. Mark DeRosa walked, prompting Joe Maddon to bring in Kyle Farnsworth to face … you guessed it, Jose Bautista. Strike one, strike two, and then Bautista singled to right field, bringing in Rasmus with the winning run.

Bautista’s WPA for the game: 1.062.

Pitchers

As I mentioned above, and as common sense dictates, pitchers can also affect their team’s chance to win a game. Unlike notable WPA games for batters, which generally take one or two plate appearances, pitching WPA accretes slowly over multiple innings. It’s hard for a batter to stand out in a game because there are at least 9 of them, whereas pitching contributions are usually spread over 3-4 pitchers in a game. Also, a single batter may come to bat 5 times in a game, but a starting pitcher faces something like 20 batters a game.

 

Below are the five games where an AL pitcher contributed the most to his team’s chance of winning the game.

5. Ivan Nova vs. Baltimore Orioles, August 31st

Nova’s line: 9 IP 3H, 0 R, BB, 5 K. Yankees win, 2-0. WPA 0.654.

Nova was injured and ineffective for the first half of the 2013 season but returned to the bigs in the summer to get a 3-2 win over the Orioles. When he next met the O’s, it was in late August, and Nova threw his first career shutout. ‘Nuff said (I already told you I’m an O’s fan).

4. Justin Masterson vs. New York Yankees, May 13th

Masterson’s line: 9 IP, 4 H, 0 R, 3 BB, 9 K. Indians win, 1-0. WPA 0.711

I don’t think WPA takes into account the kind of out that gets generated; that is, I believe that a strikeout would be worth slightly more WPA (to a pitcher) than a groundout would be, because the groundout had a higher chance of ending up with a runner on base (due to a fielding error), but WPA doesn’t take this into account. If it did, Nova’s performance would probably be worth more than Masterson’s, who struck out more batters than Nova did but let three more batters get on base (via a walk or hit).

But WPA doesn’t work that way, and although it could, I’m too lazy to take that into account. Hence we have Masterson’s stifling of the Yankees on May 13th as our fourth-biggest contribution by a pitcher.

3. Adam Warren vs. Oakland A’s, June 13th

Warren’s line: 6 IP, 4 H, 2 BB, 4 K. Yankees lose, 3-2 in 18 innings. WPA 0.775.

This is the only high-WPA performance that ended in a loss, and it’s one of only two that involves a relief pitcher. The reason is that the game in question lasted 18 innings, was scoreless and tied for 15 of them, and was decided by a single run. Since the game was at Oakland, every time an A’s player came to bat after the 8th inning, they had a decent chance to win the game. By holding the A’s scoreless for six innings, Warren gave his team’s chance a huge boost even though they lost.

2. Chris Archer vs. New York Yankees, July 27th

Archer’s line: 9 IP, 2 H, 0 R, 0 BB, 6 K. Rays win, 1-0. WPA 0.812

Chris Archer is the latest in a long line of sterling young Tampa Bay starters (although he wasn’t drafted by them). This sterling performance hints at why he’s a finalist for the 2013 Rookie of the Year award.

1. Jesse Chavez vs. New York Yankees, June 13th

Chavez’s line: 5.2 IP, 0 H, 0 R, 2 BB, 7 K. A’s win, 3-2 in 18 innings. WPA 0.857.

Yes, this is from the same game as #3 above. It makes sense; 15 scoreless innings mean that both pitching staffs are doing a great job. And when nearly 1/3 of that performance is done by one pitcher (on each team, that is) you have an opportunity for both staffs to accumulate some high-WPA performances.

Warren wasn’t bad, but Chavez was better: he pitched 1/3 fewer innings but gave up fewer hits and struck out more batters. He held the line long enough to give Nate Frieman the opportunity for a walkoff single in the bottom of the 18th inning.

What I Learned

A couple interesting tidbits stand out to me. One is that most high-WPA performances by batters are generated from one or two plate appearances. It seems to be much harder, or at least much more rare, to help your team consistently over the course of a game in the way that Kawasaki and Bautista did. If we focus just on Bautista, he doesn’t have another ranking on the WPA charts until position #77. That’s still pretty high given the 25,000 or so player-games in the season but shows that it’s hard to repeatedly help your team win single-handedly. On the other hand, the rarity of such performances is why it’s fun to examine them in story form like this.

It’s also bizarre to me that the highest-WPA pitching performances all involve the Yankees. I’m guessing that this is because their offense was so weak for much of the season but their pitching was so good. In that case, batters aren’t generating a lot of WPA, so it’s your pitchers who will be keeping your season afloat. If the offense was scoring a lot, the pitcher’s contributions would become less important, since they would be on the mound with their team in a better position to win. Of course a team could have both batters and pitchers generating a lot of WPA over a season, but that season would be some kind of unbearable seesaw between whether your pitching is good that day or your offense is.

Anyway, this has been fun, and I look forward to talking about the NL’s best performances in a later post.

* All WPA, Win Expectancy, and game event data courtesy of  baseball-reference. Individual pitch information courtesy of brooksbaseball.net.