It wouldn’t be surprising for a player at a physically demanding position like shortstop to go through a rapid decline as he enters his 30s.

Which I suppose is a plausible on age alone, but particularly in terms of offense, this really doesn’t seem to be a valid assumption. Rollins had a very distinct peak in 2007 that was, at least offensively, like one of Jeter’s above average but not career pacing seasons. He’s gotten worse in each subsequent season. By contrast, Jeter is coming off his best offensive season since 2006, during which time he did decline a bit in 2007 and 2008, but of the three, the worst was 2008, the only truly “poor” offensive year Jeter had, and a year in which still had a higher wOBA than Rollins’ career mark.

So then the argument comes down to defense, and assuming that Jeter’s career defensive season this year was as much of an aberration as Rollins’ defensive dropoff was. Rollins posted a negative RngR this year for the first time since 2004. Jeter had a positive RngR for the first time since 2002. If those numbers flip back to the career trends pre-2009, then the two even out a bit in overall value, and maybe you can make a case for favoring Rollins. But if Rollins doesn’t regain defensive wizardry, or Jeter maintains whatever improvement he appeared to make this year, I do think Jeter still projects quite a bit better offensively, and enough so that its tough to make a case that Rollins is going to be the better player moving forward. Rollins’ production is almost all based on his athleticism. He hits for power, he runs well, and plays good defense. Jeter may not do any of those things quite as well (though he did play better defense this year), but he wins in most other departments, including ability to get on base via walk and pitch selection, which are much more sustainable skills for older players than those Rollins relies on. Rollins entirely relies on things like batspeed and footspeed for production, while Jeter has skills that allow him to buffer such losses. The marginal hit on Rollins’ production through natural athletic decline is greater.

I got the same weighted WAR numbers as Eric: 5.3 Jeter, 4.4 Rollins.

Rollins WAR numbers since 2002 show a clear peak in 2007 and he has been declining since. Jeter has been all over the place. There is not much proof that he is in a “decline stage” of his career.

True, Rollins is much younger than Jeter, but he is still on the wrong side of 30. As Meddler mentioned above, they are different types of players. It wouldn’t be shocking for a player of Rollins/Reyes type that relies on athleticism to decline before and at a faster pace than a player of Jeter’s type.

I made a crude spreadsheet with the WAR data for some reason:
http://spreadsheets.google.com/pub?key=tGaKpnljRe3W9l4t3wyioiA&output=html