Win Probability Added


Imagine the White Sox have fallen behind 15 to 2, and then in the 7th inning Adam Dunn hits a solo home run. As a fan, how do you feel in that moment? You’re probably happy to see the home run, but it the Sox are still behind 15-3, so what’s the difference? Your happiness is likely to be fairly minor and short-lasting. On the other hand, if the bases are loaded and the Sox are down 5 to 2 with two outs in the 9th and Dunn hits that same home run, how does that feel? It’s different, right? You’ll be high-fiving everyone in sight and are likely to feel good the whole ride home.

Win Probability Added is a fun statistic many baseball fans are not very familiar with, one that noted statistician Tom Tango has called, “the quantification of your feelings as the game unfolds, assigned to the players involved.”

Decades and decades of games allow us (well, not us, but others, who’ve out in the time) to determine the probability of either team winning the game, from any given game situation (based on the inning, score, base runners, etc.), this is called “win expectancy (WE).” During his game recaps, Matt usually posts a WE chart from Fangraphs, as the green line rises and falls, you’re seeing each team’s chances of winning as they changed throughout the game.

Each plate appearance during a game changes the teams’ win expectancy. If Alex Rios hits a single, the Sox WE goes up, if he strikes outs, the WE goes down. Win Probability Added (WPA) tracks those changes in WE for each player. Let’s say that Alex Rios single boosts the Sox WE from 50% (.50) to 55% (.55). Rios is credited with that improvement of 5% (.05). If in his next trip to the plate he strikes out, dropping the Sox WE from 62% to 58%, that change (-.04) goes onto Rios’ WPA too: .05 – .04 = .01.

The Adam Dunn home run hit under the first scenario above will do very little to his WPA, because the Sox WE probably went from something like 1% to 2% (less than that, actually). But in the second scenario, that changed the Sox WE from say 25% to 100%, a massive 75% (.75) jump.

WPA can be tracked for individual plate appearances, added up to give you a player’s total for a game, a month, a season, or a career.

Does that make sense? I hope so. Anyway, I thought it would be interesting to see which White Sox hitters have had the biggest impacts on the team’s WE in 2012 (both for better and for worse). As with many of the more modern stats, there are a few different calculations for WPA. None of them will give you wildly different results, but for the record I’ll be using the Baseball-Reference version here.

White Sox 2012 WPA leaders (through August 16th):

  1. Alex Rios                              2.166
  2. Paul Konerko                     1.457
  3. Kevin Youkilis                     1.391
  4. Alejandro De Aza               0.689
  5. A.J. Pierzynski                   0.688
  6. Adam Dunn                        0.687

That Kevin Youkilis figure is for only his time as a member of the White Sox, giving you some sense of how big an acquisition he’s been for the team. Adam Dunn’s figure may seem low, but while the 33 home runs are great, the man has made a lot of outs this season too. Rios leads the team, but is ranked only 18th among all American League hitters (Josh Willingham is the surprise leader, at 4.86).

Here are the White Sox all-time single season leaders in WPA:

  1. Dick Allen (1972)               7.257
  2. Frank Thomas (1997)      7.199
  3. Frank Thomas (1992)      6.446
  4. Carlos May (1972)            6.362
  5. Frank Thomas (1993)      6.257
  6. Minnie Minoso (1954)    6.040
  7. Minnie Minoso (1957)    5.095
  8. Jermaine Dye (2006)       4.923
  9. Frank Thomas (1995)      4.846
  10. Minnie Minoso (1960)    4.838

You’d expect to see Frank Thomas on there, but Minnie Minoso with 3 of the top 10 season is something of a surprise, isn’t it?

Here are the 2012 White Sox leaders for single games:

  1. Adam Dunn (May 5)                       0.465
  2. Alex Rios (May 8)                             0.438
  3. Tyler Flowers (August 11)             0.436
  4. Kevin Youkilis (August 4)               0.420
  5. Gordon Beckham (May 4)            0.417

That Adam Dunn game came against the Tigers, he hit a 9th inning home run off Jose Valverde that moved the White Sox WE from 32% to 82%.

Finally, for fun, here are the top postseason games in White Sox history:

  1. Paul Konerko (Game 2 of the 2005 World Series)               0.500
  2. Joe Crede (Game 5 of the 2005 ALCS)                                     0.433
  3. Geoff Blum (Game 3 of the 2005 World Series)                  0.411
  4. Joe Crede (Game 2 of the 2005 ALCS)                                     0.408
  5. Lance Johnson (Game 4 of the 1993 ALCS)                            0.384

How many of those games can you pick out the big moment from??? At least a couple, I’m sure.

I wouldn’t use WPA as a major factor in determining the best players in baseball or to predict who’s most likely to get the team’s next big hit, but it can be fun to look through at both the seasonal and single game levels and see what turns up.