Ok, so I was having this debate on another forum, where a member was trying to convince me that this year Jonathan Papelbon was more valuable than Travis Hafner. His main argument rested on Papelbon's PRAA and PRAR (41 and 74 respectively).
Now, I did a little research, just to see where Papelbon stood, and was shocked to see that Johan Santana's PRAA on the season was a 38, 3 points lower than Papelbon. His PRAR was 103, however.
But anyway, back to the PRAA. I myself have used this statistic when evaluating worth and I see it thrown around quite a bit, but to see Santana's 2006 value appear lower than any
closer's in troubling to me.
A question regarding PRAA:
I believe it is based on an XIP (expected innings pitched) calculation. Which, I believe, is an adjustment to the innings pitched of that player based on the importance of the innings which they pitched. Papelbon's adjustment moved him from 68.3 IP to 107.9. So, the 41 PRAR is based on the 107.9.
So, if he allowed 7 ER in 68.3, it is adusted to 11 in 107.9. Add 41 to the 11 and you have 52 ER in 107.9 innings being average...or a 4.33 E.R.A.
However, since Papelbon didn't pitch 107.9 innings and only pitched 64% of that total, wouldn't his true runs above average only be 26? If he pitched the full 107.9 then you get 41, right? But he didn't pitch that many. He pitched 68.3... so, to me, it'd seem like he should only get credit for what he actually pitched. That'd put him at 26.24 runs above average.
Now, what I'm thinking is that PRAA is not an accurate measure of cross-evaluating... It looks useful in weighing Starters vs Starters, Closers vs Closers, etc. but I found this shocking when I tried to cross between the two.
Any insight into this would be awesome.