The emergence of Trevor Plouffe at AAA this year has been one of the most heavily discussed story lines amongst Twins bloggers during the 2011 season (behind only the cavalcade of injuries, and dramatic discussions of Joe Mauer's future). That level of interest is hardly surprising as the shortstop and former 2004 first round pick (20th overall) has turned the corner in a big, big way at AAA this season.
For most of his Minor League career, Plouffe has been known as both offensively and defensively deficient. A SoCal prep pick, Plouffe is in his 8th season of toiling away in the Twins Minor League system and understandably, Twins fans likely feel as though he's been there forever, yet he's still just 25 years old. As a team that tends to move players just one level per year, Plouffe didn't first reach AAA until 2008 and didn't spend his first full season there until 2009.
Throughout his career, Plouffe's strengths and weaknesses have always been pretty readily apparent. As a career .257/.320/.406 hitter with an ISO of .148, a strikeout rate of 18.4%, and a walk rate of 7.8% we can see that he neither made enough contact to hit for average, nor drew enough walks to post respectable on-base numbers. His one real offensive strength was his ability to hit for power, an attribute that had been improving the past few years, before breaking through in a big, big way this season.
Defensively he's always had the raw tools to be a quality shortstop, and he still does. I'd rate his lateral range as slightly above average for a shortstop, and he's got the arm to make strong throws from deep in the hole. The problem is that his hands are not soft and he'll boot more of the routine plays than you'd like to see out of a shortstop and his arm is rather scatter-shot. In short, he'll probably get to somewhat more balls than your average shortstop, and he can make some spectacular plays, but he just hasn't been very consistent.
The reason for excitement with Plouffe however has precious little to do with his defense, but rather the offensive breakout he's experienced this season. After a career of Minor League mediocrity Plouffe is hitting .305/.379/.650 for an extremely impressive 1.029 OPS. He's mashed 15 home runs in just 181 at-bats (he's previous career high was 15 in 402 ABs last season), and has 29 extra base hits overall. He's walking more at an even 10.0% and his .300 BABIP suggests there isn't anything particularly flukey about his contact rates (though a .345 ISO is laughably unsustainable).
Looking at Plouffe's career progression we've seen steady improvement in his power as his ISO has improved from .097 to .186 last year, with marginal improvements having been made at essentially every stop. Generally speaking that isn't particularly unusual - power tends to develop with age and physical maturation after all - but a .187 ISO from a shortstop is very good (it's actually just pretty good in overall), and given his performance this season it seems likely that he's yet to realize his full power potential.
One thing that's held Plouffe back offensively is that unlike so many other well regarded prospects who routinely post BABIP marks in the .350 range during their MiLB careers (the sub-par defense is the Minors allows a higher % of balls in play to become hits), his career BABIP is a well below average .288. Of course a huge part of that is because he just doesn't hit many line drives. For his career his LD rate stands at just 14%, well below average. This year that rate has increased to a career best 17%, but even that mark isn't very impressive. On top of that he hits a ton of ground balls and with just average speed, that doesn't translate into many infield hits.
Given his propensity toward low line drive and BABIP marks, and a strikeout rate that is just average or slightly worse than average, the odds of Plouffe ever consistently hitting over .250 or so just doesn't seem very likely. However if he can continue to walk at a rate closer to 10% that could translate into a .250/.325 type of AVG/OBP. Add in power that could quite possibly be in the .200 ISO range and that gives you a hitter with an overall triple slash of .250/.325/.450 - or a .775 OPS - and seeing as how the MLB average for shortstops has been a paltry .698, it's not hard to see how impressive that mark really is.
Offensively Plouffe reminds me a lot of J.J. Hardy, who obviously had a very brief career with the Twins last year. Both players have plus power for their position, but have posted relatively weak AVG/OBP numbers due to similar LD/GB/FB rates. Hardy of course has always been a legitimately plus, and seriously under rated defensive shortstop, which Plouffe most certainly is not. But if Plouffe can simply manage to be a league average shortstop (and I think UZR would grade him out as one) his plus offense would make him a very rare commodity - a legitimately league average or better shortstop.