I keep seeing the Jeter comps, and they fit, but Jeter struck out a lot more than Pedroia does. Earlier tonight I started thinking about George Brett. Brett in his early seasons would usually go somewhere around 20-20 with a .300-.330 BA and more walks than strikeouts. Brett wasn't as efficient a basestealer as Pedroia, and hit with maybe a little more power, but would it be out of line at this point to start making that comparison?
Brett is an interesting comp that would not have occurred to me. A little more power than Pedroia will probably ever show, but otherwise pretty close.
I hate to be caught agreeing with
CHB, but I think Pete Rose is also a good comp. Like Rose, Pedroia is a line-drive, contact hitter with a good BB/K ratio (though Rose had a bit more of both), 40 double/15 HR kind of power, and a reputation for hustle and manic energy. Both were known as aggressive but smart baserunners; Pedroia is the better basestealer so far, though I think their actual foot speed is/was pretty similar. Both started as second basemen, and though Pedroia so far looks like a much better 2B than Rose, who was moved to the outfield at 26, their defensive strengths are similar, i.e. quick reactions and a surprisingly strong, accurate arm for their size.
Rose won ROY in 1963 at age 22, and after a bit of a sophomore slump, came back in 1965 with an age 24 year fairly comparable to Pedroia's 2008; Rose walked more and hit for less power, and didn't steal as much or as efficiently, but overall the years compare pretty well when you allow for the different offensive environments. Rose's 1965 OPS+ was 127; Pedroia's is currently 124. That year Rose finished 6th in the MVP balloting (4th among non-pitchers).
The main differences between Pedroia and Rose so far are all in Pedroia's favor: a bit more power, a bit better baserunning, better defense, and an attitude that matches Rose's intensity while seeming to avoid most of his abrasiveness. Of course it remains to be seen if Pedroia can hold up at this level for a long career the way Rose did. But he's starting off on more or less the same trajectory.