Win Probability Added has been gaining steem for a few years now, but it’s popularity really seems to be boiling over this season. I’m a big fan of the statistic for a variety of reasons, none of which are because it carries any significant contribution to the discussion of who’s a better player:
- WPA’s methodology is still being worked out. It’s a fun puzzle to figure out how to calculate WPA and leverage. (Hey, I’m a math geek.)
- WPA is a foundation for showing that modern bullpen usage is suboptimal. Teams could probably squeak out another few wins each year just by deploying their relievers better.
- WPA lends itself quite well to visual presentation. Graphs like these are a nice change of pace from the traditional game writeup.
- WPA reflects the fan’s sense of drama while watching a baseball game. A homerun hit in the first inning doesn’t evoke the same emotional response as a walk-off homer.
- WPA accounts for how much each player actually changed his team’s chances of winning a game. There’s no guessing or estimating as to how much a single generally helps a team. A specific single in a specific situation has an exact value to a team.
- WPA is the ultimate MVP metric.
I know Dave Studeman disagrees with that last statement, so let me explain. In my mind we should not be awarding an MVP — it’s just too vague an award, one that I’ve stopped really caring about. What we should be awarding is a Best Player award to honor the player that achieved the highest level of performance — the player that would be picked first before the season if every general manager was omniscient. Best Player would not include team-dependent influences such as RBI, game-winning HRs, or the “skill” of carrying a team to the playoffs.
But since the baseball writers don’t award the BP and instead hand out MVPs, we can at least limit the damage using WPA. Most voters see the MVP as the player who did the most to help his team win. That includes being clutch and performing when the possibility of making the playoffs hangs in the balance. Isn’t that exactly WPA?
Actually, not quite — WPA is the next-to-ultimate MVP metric. The ultimate would be Playoff Probability Added — a combination of WPA and playoff odds. Just like WP is the probability of winning any particular game given the current game situation, PP is the probability of reaching the playoffs given the current game situation and league standings. Helping your team win a game early in the season isn’t as dramatic as hitting a walk-off homer on the last day to clinch the Wild Card. And hitting a walk-off homerun on the last day for a team in last place wouldn’t exactly be MVP-caliber material.
Conveniently, Baseball Prospectus posts a Playoff Odds report that presents the likelihood of each team making the playoffs. For each game, you’d simply need to multiply each player’s WPA by the difference in playoff probabilities between his team winning and losing that game. Sum over the whole season and you’d find out which players did the most towards increasing (or decreasing) their team’s chances of making the playoffs. Hello, MVP.
I find it ironic that the ultimate MVP stat is perhaps the most convulated, math-geekified calculation I can think of. I mean, if MVP voters would pay any attention to it, they’d probably first accept that Best Player is a much better award than MVP. It’s just a fun little toy. Like WPA.
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Sky is a baseball fan and racket sport afficianado living in upstate NY. His favorite color is orange and is just about ready to give up on his life-long dream to become the next Magnus ver Magnuson (World's Strongest Man). His favorite baseball teams are the Yankees and Red Sox, proving that there's hope in the Middle East. 
April 27th, 2006 at 7:04 am
Hey Sky, let me try to explain more fully why I don’t think it’s the ultimate stat for MVP.
When a reliever enters a game in a high-leverage situation, he deserves credit for that, because he’s being called on to perform in a key spot. He also had nothing to do with the game prior to entering it.
But when Andruw Jones hits a game-winning home run in the bottom of the ninth after going 0 for 3 or 4, he gets a big boost from a high-leverage situation that HE HELPED CREATE. IOW, by “waiting” to hit his home run, he inflated his WPA.
Now, players do receive negative WPA points when they don’t hit earlier in the game. But it’s at least arguable whether the system adequately reflects that fact. And philosophically, it doesn’t seem right to me to give someone big-time credit for something when they had an impact on the circumstances of the credit.
One last thing: starting pitchers are just plain undervalued by WPA. That’s my opinion of course, and I’ve never seen an entire year of WPA stats for starters so I could be wrong. I’d love to see how a Dwight Gooden in 1985 would do in total WPA.