Win Probability Added (WPA): Quantifying “Clutch” – Romantic About Baseball
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Win Probability Added (WPA): Quantifying “Clutch”
July 30, 2019 category No Comments;

This is the fourth in an ongoing series about understanding advanced statistics in baseball.  Each volume will take an advanced stat, explain it, and contextualize it in the hope that the basic fan can better understand the numbers that drive the game today.

Game seven, and it’s the bottom of the ninth, bases loaded, down by three.  Anyone who has ever played baseball in their back yard, living room, or on the sandlot has fantasized about that moment.  Insert your favorite teams jersey, and your rival pitcher on the mound, and you are in the moment.  It’s been said that it takes a certain type of player to perform in those all-important situations, where the game is on the line.  We say they “have ice in their veins”, they “thrive on the pressure”, or are simply “clutch”.  Those that fail are marked as players that “don’t have what it takes” or that they “can’t take the spotlight”.  It’s always been a sort of “eye test” way of evaluating how a player performs in situations that can alter the entire outcome of a game, and there’s no real perfect way to quantify these sorts of things, because there’s so much that goes into it.  Baseball isn’t as cut and dry as other sports, where a clock ultimately dictates the outcome, or it’s an individual effort as opposed to a team game, so it’s not exactly easy to say how a single player can affect the entire outcome of a single game or series.

Let’s try though, shall we?

What is it?

sandman

WPA or “Win Probabilty Added” is a way to factor how an individual player raises or lowers his teams probability of winning a game.  To figure out a players impact, you have to first place him in the given situation, and look at his teams win expectancy.  Win Expectancy is a percentage of a teams odds of winning the game in that situation.  Per Fangraphs:

“If the batter flies out on the first pitch of the game, the home team’s WE goes up from 50% to about 52%. This means that the pitcher who induced the out gets a WPA of +0.02 and the batter gets a WPA of -0.02.”

So you can see, for every action that RAISES one teams percentage, the reciprocal affect takes place for the other team.  Over the course of a single game, a player can raise or lower that number, as well.  For example, if that same player that flew out to lead off the game goes on to gather three more hits, including the game winner, obviously his -.02 is wiped out and becomes a positive.

The stat is context dependent, meaning that the weights change depending on the situation of the game.  A player has more direct impact on a 2-2 game in the ninth inning, than say a batter that hits a home run in a game that his team is already losing by 8 runs, due to differences in the win expectancy.

What Does it Tell Us?Image result for bernie carbo

WPA can tell a statistical story of a game, series, or even a career in a way that better illustrates not just the players skill level, but how a player delivered in situations that mattered most.  In the past, these players have been referred to as “clutch” players, without any sort of background or way to measure it.  Keith Law gave a dubious endorsement of it in his book Smart Baseball (Which, If I may say so, is great reading.):

..”The Good thing about WPA, as opposed to the typical codswallop claims of players who are clutch or who ‘smell an RBI’ or ‘know when to bear down’, is that WPA is deaf to your excuses.  WPA accepts no rationalizations like luck or bad defense or anything of the sort.  WPA does not care for your explanations of context or your what-ifs.  IF a reliever comes in with men on base and gets a couple of hard-hit outs without letting any of those runners score, then his WPA for the game is going to be positive-the closer the game, the more positive it will be.  His team had a certain chance of winning the game before he entered, and had a better chance after he was done…” (p. 158)

Law goes on to say that while the stat itself is a good way to tell a story, it shouldn’t necessarily be used as a way to evaluate players as a whole.  What Law hits on here is that WPA gives objective facts to otherwise subjective situations.  It takes moments like Bernie Carbo in 1975, who hit the game tying home run in the 8th inning to give the Red Sox new life in what many called “The Greatest Game of All Time”, and gives us an objective comparison to David Freese, who single handedly staved off the Texas Rangers with a triple to tie the game, then a Home Run to end it (I have argued that the latter game exceeds the greatness of the former on Baseball Almanac).  That Comparison looks like this:

  • Bernie Carbo WPA: 0.442
  • David Freese WPA: 0.964

So by definition, Freese was twice as integral to his team winning his game than Carbo, despite the circumstances.  To be fair, though, Carbo was brought in as a pinch hitter.  Let’s look at David Ortiz in the infamous 2004 ALCS against the Yankees in game 4, when he famously lifted a pitch from Mariano Rivera over the right field wall, allowing the Red Sox to live another day (and eventually a few more)..

  • David Ortiz: .234
  • David Freese: .964

That’s not so much to take away Ortiz’s herculean performance that would eventually lead the long tortured Red Sox to their first title in (literally) a lifetime, it just allows us to appreciate how objectively appreciate how amazing Freese’s performance was, and how directly he affected the outcome of the game.

Makes you wanna watch it again doesn’t it?  Go ahead…

So Who’s the Greatest Ever?

bbonds

Barry Bonds (127.66)

For a guy that has usually carried a reputation as being flacid (see what I did there?) in the postseason, he was actually a one man force when his team took the field.  His very presence in the lineup put teams in precarious situations, and consistently put his team into positions to win games.  Of course, as history also shows us, those teammates would fail him more often than not, but the objective measurement tells us that no one in the history of baseball helped his team win more than Barry Bonds.

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