If you ever come into contact with any of Philadelphia's wonderful sports media, then you're probably aware that seemingly everyone's favorite words these days are "righthanded bat" and "Hunter Pence." Just the other day, I heard one radio host explain that the key to winning in baseball is developing cost-controlled players and managing contracts (OK) and that because of this fact, the Phillies need to think seriously about trading Domonic Brown given how great his trade value is as a result (umm) - but of course, you would never give up Brown for just any player, you would only part with him if it was to get a cornerstone righthanded bat like Hunter Pence.
I don't know when everybody started to think of Pence as (to borrow Joecatz's words) a 24-year-old Ken Griffey, Jr., but he's being wildly overrated by way too many Phillies fans.
This isn't to say that he isn't a good player - he is. His wRC+s from 2008 through 2010 were 101, 115, 112. Throughout those years, he hit for a decent average, drew an acceptable number of walks, and hit exactly 25 home runs in each season. He had pretty good UZRs too and he accumulated a very respectable total of 10.9 fWAR. Still, I doubt that there was a single person in Philadelphia who would have thought of Pence, on April 1, 2011, as a "cornerstone piece."
The only reason why some people now feel that way is that he's having a career year this year (139 wRC+ and on pace for ~4.7 WAR). Now, there isn't necessarily anything wrong with that. Pence is 28 years old, and it isn't at all unusual for guys to "get to the next level" around that age. He's probably still got a few seasons left in his prime and he has two arbitration years before he reaches free agency, so if the 2011 Pence is really a Brand New Pence, then he might very well be something that kinda-sorta resembles a cornerstone.
But here's the problem. If you drill down a little deeper into Pence's stats, this is what you'll find:
First, his walk rate hasn't increased, while his strikeout rate is the highest of his career (20.5% compared to a career average of 18.2%)
Second, his power numbers are down, as his ISO is the lowest of his career (.166 compared to a career average of .190). Of course, this is mitigated by the MLB-wide decline in power numbers, but at the very least, his power hasn't improved much.
So why are his stats better this year than ever before? All because of batting average (.318, compared to a carer mark of .291). And because his strike zone command and his power haven't improved, his improvement in batting average is all attributable to BABIP. His career figure is .328. This year, he's at .381.
Which, again, isn't necessarily disturbing. Hitters actually do have some control over BABIP (a lot more than pitchers do, at any rate) so it's theoretically plausible that Pence just got better at it at age 28. Also, while his BABIP hovered right around the league average throughout the 2008-2010 period, he posted a .377 over 108 games in his rookie year in 2007 (.322 overall BA), so a high number from Pence isn't totally unprecedented. Maybe Pence got a lot more adept at hitting line drives at the expense of hitting fly balls. If so, that would explain why his power has gone down but his batting average has gone up.
But that doesn't seem to be what's actually happening. Pence's line drive rate has, in fact, gone up this year - but not by that much. See below.
YMMV here, but I have my doubts that shifts of three or four percentage points from one batted ball category to another are enough to explain a 70 or 80 point differential in BABIP. Pence is still basically what he's always been - a groundball hitting machine. After placing in the Top 20 in GB% among MLB qualifiers in every previous qualifying year of his career, this year he's 22nd. That might be consistent with a .380 BABIP if you're Ichiro in his prime, but not so much if you're Hunter Pence, prime or no prime.
In all likelihood, what Pence is doing is unsustainable, and he isn't "really" all that different of a player in 2011 than he was in 2010, 2009, or 2008. If his current trade market value is based on his 2011 performance, then chances are his price is too high and if you pull the trigger, Ed Wade will take you to school.