Comparing Jhonny Peralta to Stephen Drew


No one seems to be exceptionally excited about the Jhonny Peralta acquisition. Responses seem to vary from “I hate it” to “it’s okay.” But what if it had been Stephen Drew that the Tigers had traded for? I’m confident that there would have been a near unanimous response of “LOVE IT!” So what is it that separates Stephen Drew from Jhonny Peralta (besides ten months in age)?

I’m going to look at this question from a purely statistical standpoint. I’ll use wOBA and UZR to assess their offensive and defensive abilities and then combine the numbers into runs for a single number comparison (this will be similar to the other shortstop posts I’ve done). When assessing defense, I’ll only consider Peralta’s numbers from his seasons at the shortstop position, hopefully this will give us an “apples to apples” comparison.

I’ll start with their respective career numbers. Stephen Drew has been pretty much league average at the plate for his career with a .331 wOBA. Jhonny Peralta has been a shade worse at .326. The difference in offensive potential between these two numbers is 2.8 runs in 650 plate appearances (approximately one season).  On the defensive side, Drew has been about 7.2 runs below average (per 1300 innings) according to UZR. Peralta has been about 6.1 runs below average for his career. Obviously, this difference is about 1.1 runs in favor of Jhonny. So, according to their career offensive and defensive metrics, Drew would add about 1.8 runs of value more than Peralta would over the course of the season. Whoop-de-doo. (More after the jump)

But career numbers isn’t necessarily the best way to determine relative values of two players. Let’s look at the recent history of 2007-2010 (three years plus this season) to see if we can get a different look at these guys. On offense, the three year difference is quite small. Drew leads Peralta by 0.002 wOBA points, which is good for 0.8 runs of offense in a season. On defense, Drew has been 6.5 runs below average (again, per 1300 inning season), and Peralta has been 5.0 runs below average (only considering his time at shortstop). Put these numbers in a blender, and we’d expect Peralta to contribute 0.6 runs more than Drew over the course of a full season. Another whoo-de-doo.

We do see a big difference, however, when only considering this season’s numbers. Drew has had a big advantage on offense, and he’s also having one of his better defensive seasons (according to UZR). Drew leads Peralta by .022 wOBA points (12.4 runs per season), and 11.7 runs of UZR (I had to use Peralta’s 2007-2010 UZR average since he didn’t play short this season for Cleveland). That’s good for a total advantage of just over 24 runs (2.4 wins) for Stephen Drew. This is the most significant difference we’ve seen between the two players, but unfortunately it’s probably the least statistically significant one. One standard deviation of wOBA due to random variation is .026 points in 380 plate appearances (and we’re showing a .022 difference). UZR is also notorious for giving poor readings in small sample sizes (less than three or four seasons worth of data).

In general I tend to trust either career numbers or a three year average over a single season’s worth of data, but I’m not going to tell you which of the data sets you should go with. I think Peralta could handle the shortstop position in an everyday role, but his disappearing bat is a big concern. If he can pick up the pace at the plate and even approach his career numbers, he’d be a valued member of the 2011 version of the Tigers. For as similar as their career numbers are I’m surprised that there’s been so much clamor for Drew and so little interest in Peralta. Maybe I’m off base?

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Tags: Jhonny Peralta Stephen Drew

  • http://motorcitybengals.com John Parent

    That’s some shocking stuff there Matt. Like the others you referenced, I am on the “it’s okay I guess” side of this deal, but would have been all about getting Drew. I didn’t run the numbers, obviously, so I appreciate your take here.

    The one thing I would caution is weighing too heavily the defense. Given that Peralta hasn’t played short at all this year, and not much last year, you have to assume there’s a reason for that (apart from the presence of Cabrera– he’s missed a lot of time and Peralta still hasn’t played short).

    I admit that I haven’t seen Drew play often enough to get a true feel for his glove and range, but having seen plenty of Peralta at short over the years, I was never all that impressed. I do like his bat, however, even if he’s not the offensive threat he once was, and having Inge back at third cuts down on the amount of ground he (Peralta) would have to cover at short.

    The more I think about it, the more it seems extremely possible that this trade was made with an eye on 2011 as well as this year. Peralta will have a two month audition to show the Tigers he can be the guy they need next year and if he plays well, I could see the Tigers picking up his option.

    • http://sidelionreport.com/ Zac Snyder

      I will admit that I would have been a lot more excited about Drew as well. I think there is a perception that Drew is quite a bit younger than Peralta but, as Matt points out, it is just a ten month difference in age. That was the biggest shock to me and I’m sure a lot of other people didn’t realize that either.