Slo, I don't think age 28 is the normal year to begin a decline, but it certainly is possible. Two things in Jacoby's favor:
1) He has not played many 162 game seasons, so he may peak at age 29-30.
2) I think he is in better "baseball shape" now than at ages 24-26.
I think if you graphed Jacoby's production into a normal S-Curve projection, his 2011 season may not look like a fluke at all.
In a limited 2007 season, he had a .394 OBP.
The S-Curve model correctly projected a decline in year 2 (.336).
Year 3 showed the expected uptick to .355.
Had he not been injured in 2010, one might have graphed a point of about .365.
Had that happened, his .376 2011 OBP was right on track.
Normally players peak at 29-30 unless they they have played 7-8 full seasons by age 28, and a decline might occur sooner.
One could easily project an OBP above .380 for 2012, in fact, by the model, it seems more likely he improves than declines, but I'm not so sure he will.
Looking at Slg% and his body changes, I would expect a decline in 2012.
His Slg% went from 509 to 394 to 415 to injured year to 552. Thats a huge spike and probably not sustainable.
If I had to project Jacoby's next 2 years right now, I might go something like this: (OBP/Slg%)
I admit, this is pure speculation. He could hit 40 HRs next year. He could decline to .290/.360/.440/.800.
I'm not sure about your percentage chances of Sizemore, Reddick, and Kalish of topping .780, but I do agree, the cahnces are one of the 3 will, but if we trade Ellsbury, we will need 2 of them to do it. I'd bet against that.