Larry Mahnken and SG's

Replacement Level Yankees Weblog

"Hey, it's free!"

The Replacement Level Yankees Weblog has moved!  Our new home is:

Larry Mahnken
Sean McNally
Fabian McNally
John Brattain

This is an awesome FREE site, where you can win money and gift certificates with no skill involved! If you're bored, I HIGHLY recommend checking it out!


Disclaimer: If you think this is the official website of the New York Yankees, you're an idiot. Go away.

September 28, 2005

Which performance is more valuable?
by Larry Mahnken

Here's why it's stupid to use Win Probability charts to determine value.

Extreme situation #1:

Visiting team's leadoff hitter leads off with homer, the rest of the lineup goes down in order, their only baserunner being that leadoff homer.

The starting pitcher pitches a shutout, and wins 1-0.

Extreme situation #2:

The first 25 batters for the visiting team go down in order, then the #8 and #9 hitters single, putting runners on first and third with one out. The leadoff hitter flys out and the #8 batter scores from third.

The starting pitcher pitches a shutout, and win 1-0.

Now, in Situation #1, the leadoff batter went 1-4 with a homer, a run scored and an RBI. He was literally the entire offense for his team. His Win Probability added for the game is .022, and the WP added for the homer is .060.

In situation #2, the leadoff batter went 0-3 with a sac fly, 0 for 4 PAs, with an RBI. His Win Probability added for the game is .060, the WP added for the sac fly is .179.

The fly ball was worth three times as much as the home run. This is not a home run being worth three times as much as another homer, it's an out being worth three times as much as a homer. In a game that finished exactly the same.

The starting pitcher in Situation #1 had a WP added of .887, pitching the entire game with a 1-0 lead.

In Situation #2 the starting pitcher did exactly the same thing, only this time he was pitching in a 0-0 game in every inning except the ninth. A run allowed in Situation #1 in any inning would have merely tied the game, a run allowed in any inning but the ninth in Situation #2 would have put the team behind.

In Situation #2, the pitcher had a WP added of .763.

So, somehow, the pitcher was less valuable pitching in a tied game than with a lead. Nifty stat this is.

Here's a stupid stat: In Situation #1, the seventh batter never got on base. He went 0-3. Three outs. Was the last out in every inning he batted, in fact.

He added .007 WP with his bat.


See, recording the changes in Win Probability doesn't record the value of a player's performance, because value is the number of runs he created. The initial basis of tracking game states is noble -- a run in a 5-4 game is obviously far more valuable than a run in a 15-4 game. But the 5th run is not more valuable than the first run. They're worth exactly the same amount.

Win Probabilty measures leverage. It's not the same thing. If you're going to weight the value of performance by the leverage of the situation they occur in, then you have to weight games that way, too. A win in April doesn't have as much leverage on the outcome of the season as a win in September, so why should they count the same?

Because they do count the same, that's why.