Win Probability Added (WPA) measures how much impact specific plays had on the outcome of each game and assigns that value to the individual players responsible. For example, hitting a grand slam in the seventh inning when the score is already 10-2 has less WPA value than drawing a walk to lead off the ninth inning of a 2-2 game. The grand slam didn’t have much impact on the likely outcome of the game, whereas the walk had a major impact on each team’s chances of winning.
There are much better and longer explanations of WPA than that one, of course. If you’re interested in learning more about it, Dave Studeman‘s WPA primer at The Hardball Times is a good place to start, and both Fan Graphs and Baseball-Reference.com offer tons of information on the subject. It’s far from a perfect stat and is not meant to definitively prove how valuable each player has been, but WPA is an interesting tool to use in looking back at what has already taken place.
It’s important to note than WPA doesn’t measure any defensive contributions, which means that strong defenders don’t receive full credit for their value. Beyond that, WPA doesn’t place offensive contributions in the context of position, so an .850 OPS from a catcher or shortstop is treated the same as an .850 OPS from a designated hitter or left fielder. There’s nothing that can be done about measuring defense via WPA, but it’s relatively easy to put the numbers in better context by using positional adjustments.
With the help of Fan Graphs creator David Appelman, I’ve taken the Twins’ raw WPA totals for April and adjusted them based on the MLB average at each position. Most adjustments are minimal, but starters are given a boost relative to relievers and hitters who play up-the-middle positions are given a boost relative to hitters who man corner spots. The end result is a sort of adjusted WPA (adjWPA), but before getting to that, let’s first take a look at the raw totals through April 30:
As you can see, the offensive totals for April weren’t pretty. Only Justin Morneau, Joe Mauer, and Craig Monroe provided a positive WPA — with only Morneau significantly above average — and the team as a whole batted just .260/.305/.362 while racking up -2.00 WPA. Seeing Morneau atop the list isn’t news, but it’s surprising to see Michael Cuddyer at the bottom given that he missed over half the month with a finger injury and hit a decent enough .297/.350/.405 when he did play.
Cuddyer’s low WPA basically comes from two games (April 3 and April 25) in which he combined to go 1-for-10 while leaving 12 runners on base. He had -0.58 WPA between those two games, but 0.11 for the rest of the month. Monroe is the opposite, because on April 22 against the A’s he went 3-for-4 with three RBIs, including the game-tying homer, producing enough WPA (0.32) to leave him as a positive contributor for April despite going 9-for-43 (.209) while accumulating -0.22 WPA the rest of the month.
I’ve heard it said that Carlos Gomez‘s overall struggles in April were lessened by his “single-handedly” winning games. While hyperbolic, that’s actually true to some extent, given that Gomez had four games with at least 0.10 WPA. To put that in some context, Morneau totaled six such games in April despite a vastly superior overall WPA. However, along with four huge games Gomez also had six games with WPA worse than -0.10. He was either very good or very bad, and the end result was -0.34 WPA.
Twins hitters combined for -2.00 WPA in April, but the pitching staff nearly balanced that with 1.50 WPA. Taken together that equals -0.50 WPA or a half-win below average, which is what the Twins were by going 13-14 in April. Joe Nathan led the way by converting 9-of-9 save chances with an 0.82 ERA in primarily big-pressure, high-leverage situations. Dennys Reyes was almost flawless, throwing nine scoreless innings while allowing just one of a dozen inherited runners to score.
However, Reyes totaled “only” 0.65 WPA because he faced 30 percent fewer hitters than Nathan and worked in spots that weren’t quite as crucial. Pat Neshek also worked in high-leverage situations and held batters to .209/.255/.395, but had two disastrous appearances, totaling -0.45 WPA on April 7 and -0.54 WPA on April 14. Aside from those two games, his WPA for April was a Nathan-like 1.03, but the value of WPA is that what you do in crucial situations has a huge impact.
Relievers were the Twins’ strength in April, as the bullpen combined for a 3.54 ERA and 1.06 WPA over 84 innings. The rotation was more of a mixed bag, although as a whole, the starters posted 0.45 WPA. Nick Blackburn was fantastic at 0.87, and both Scott Baker (0.41) and Boof Bonser (0.29) checked in solidly above average, but Livan Hernandez was well below average at -0.28 and Francisco Liriano was a mess at -0.67.
After looking at the Twins’ raw WPA totals through April 30, let’s switch to the adjusted numbers once each player is compared to the MLB average at their respective position. In other words, Morneau is compared to first basemen, Mauer is compared to catchers, Blackburn is compared to starters, and Nathan is compared to relievers. Positional adjustments don’t cause any huge shifts yet because of the limited number of games and plate appearances involved, but there are some changes:
|Joe Nathan||+ 1.17||Matt Tolbert||– 0.03|
|Nick Blackburn||+ 0.92|| Matt Guerrier||– 0.13|
|Dennys Reyes||+ 0.62||Kevin Slowey||– 0.16|
|Justin Morneau||+ 0.45||Denard Span||– 0.16|
|Scott Baker||+ 0.45||Delmon Young||– 0.21|
|Joe Mauer||+ 0.34||Livan Hernandez||– 0.23|
|Boof Bonser||+ 0.34||Juan Rincon||– 0.23|
|Craig Monroe||+ 0.04||Brendan Harris||– 0.24|
|Pat Neshek||0.00||Brian Bass||– 0.24|
|Brian Buscher||0.00||Adam Everett||– 0.25|
|Bobby Korecky||0.00||Carlos Gomez||– 0.31|
|Nick Punto||– 0.34|
|Mike Lamb||– 0.35|
|Jason Kubel||– 0.37|
|Mike Redmond||– 0.38|
|Jesse Crain||– 0.46|
|Michael Cuddyer||– 0.53|
|Francisco Liriano||– 0.65|
Once positional adjustments are made, only eight Twins ended April with positive WPA, which is a low total even considering the team’s 13-14 record. Nathan, Blackburn and Reyes led the top-heavy WPA distribution, while Morneau and Mauer were the lone hitters to contribute significantly above average for their position. Beginning May with four wins in five games has quickly changed the WPA picture, but this was the first of my planned month-by-month looks at WPA throughout the season.
Outside Swing Percentage
Fan Graphs also tracks a new stat called Outside Swing Percentage, which is defined as “the percentage of pitches a batter swings at that are outside the strike zone.” So far this year, Vladimir Guerrero has the league’s highest Outside Swing Percentage at 43.8 and Jason Giambi has the lowest at 9.2, while the MLB average over the past three seasons has been 22.9. Here’s how the Twins’ hitters stack up when it comes to swinging at pitches outside the strike zone.
Just four of the 11 hitters who’ve come to the plate at least 40 times for the Twins this year have swung at a lower percentage of pitches outside the strike zone than the MLB average. Among all American League hitters with enough plate appearances to qualify for the batting title, only Guerrero (43.8) and A.J. Pierzynski (38.4) have a higher Outside Swing Percentage than Gomez (38.3) and Delmon Young (36.2).
At the opposite end of the spectrum, among batting-title qualifiers Mauer (16.9) is the lone Twins hitter with an Outside Swing Percentage under 20.0. Meanwhile, the AL’s other 13 teams boast a total of 33 such hitters for an average of 2.5 per team. Talk of “plate discipline” often refers to drawing walks, and the Twins have fewer free passes than any team in baseball by a wide margin, but Outside Swing Percentage breaks that down even further and shows an incredibly impatient, undisciplined offense.
Oh, and the Outside Swing Percentage numbers shown above are from before the team’s non-Mauer hitters went 0-for-26 with one walk against Gavin Floyd and the White Sox Tuesday night. After watching Mauer narrowly save the Twins from being no-hit by Floyd, acting manager Scott Ullger summed up an offense that ranks second-to-last in runs: “I thought the umpire might have had a tight strike zone and we just didn’t allow him to walk us.”
Go-Go Cycle (Baseball is a Funny Game)
Of course, one night after Mauer’s double with two outs left saved them from being no-hit by a guy with a 5.61 career ERA, the same offense that ranked as the league’s second-worst erupted for 13 runs on 16 hits (and four walks!) against Mark Buehrle, who had been 20-10 with a 3.69 ERA versus the Twins. As if that weren’t enough, Gomez hit for the Twins’ first cycle since Kirby Puckett in 1986, Nick Punto collected five RBIs, and Hernandez took a shutout into the ninth inning.
And people wonder why I love baseball so much.
Gomez was hitting .230/.247/.310 prior to being benched for one game on April 23. In eight games since then, he’s gone 13-for-30 (.433) with two homers, five total extra-base hits and four steals. He’s now up to .282/.306/.427 in 28 games overall, which along with excellent work on the bases and strong defense in center field is enough to make up for a hideous 29-to-3 strikeout-to-walk ratio. And to think, just a couple weeks ago some idiot wrote that Gomez “isn’t an MLB-caliber hitter.”
That same moron has repeatedly suggested that the Twins made a mistake by signing Hernandez, but after last night’s complete-game win he’s 5-1 with a 3.83 ERA overall and 5-0 with a 2.76 ERA if you look past his brutal start against the Rangers on April 27. Oh, and the Twins are in sole possession of first place at 17-15, although to be fair to the aforementioned doofus he did predict back in March that the team would have a winning record when many others had them pegged for last place.