Thursday, January 28, 2010

A List (Continued)

Following up on the prior post...

Of the 174 players listed, 89 of them had a higher wOBA in their age 35 season and 85 of them had a higher wOBA in their age 36 season.

Congratulations to fgasparini for coming the closest, although I don't reward imprecision so since he hedged his guess he gets NOTHING.

As far as the purpose of the post, sam kind of got it. We tend to think about trends in baseball as significant, and we think linearly. We should not really do that, because the data doesn't really show any predictiveness in trends.

The average player is typically at his most valuable in his late 20s. By the time he hits his mid-30s, he'll have lost somewhere between 10-15% of that value. But it's NOT A LINEAR decline. He may go from a wOBA of .345 at age 28 to a wOBA of .302 at age 35, but it's not necessarily going to happen by losing .043 points of wOBA every season. It also doesn't mean that we should expect him to be worse at age 36 than he was at age 35, because over-weighing one season is silly.

So yes, Randy Winn at age 36 is almost certainly not as good as Randy Winn was at age 28. But just because he had his worst season as a regular at age 35, it doesn't mean he's going to be even worse at age 36.

While the list of players I chose is going to have some selection bias (if a player was really bad at age 36 they wouldn't have gotten 300 ABs), I think/hope it illustrates my point. There's a 40-50% chance Winn will be better at age 36 than he was at age 35, and complaining about signing him because of a poor 2009 is really just complaining to complain.

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