Martin Perez's elbow injury that will require Tommy John surgery and put him out until at least the all-star break in 2015 was devastating to the Texas Rangers, both on the field with depth and off the field with an injured psyche.
You might look at Perez, one of the Rangers' top prospects for years, and middle-of-the-road prospect Nick Tepesch and think they're not similar at all — not even on the same plane. But not so fast, folks.
What if we told you losing Perez and replacing him with Tepesch isn't going to make all that big of a difference? Well, we're not telling you that, because that's hard to say, but the fine folks at FanGraphs put together some data that shows that might very well be the case.
While he’s pitched fewer than half as many innings, Tepesch has posted a lower walk rate and a higher strikeout rate while generating essentially the same rate of ground balls when batters do make contact. And Perez doesn’t really have much of a case on quality of contact either; Tepesch has a slight edge in inducing infield flies, and they have nearly identical rates of hits on balls in play. The entirety of Perez’s ERA advantage comes from when they’ve allowed those hits to occur, as Tepesch has posted a .288 BABIP with the bases empty, a .321 BABIP with men on, and a .376 BABIP with runners in scoring position.
There’s just no reason to think that kind of split is indicative of any kind of fundamental flaw in Tepesch’s arsenal, and over a larger sample, those numbers will regress back to something more normal. In the areas that better measure a pitcher’s skills, Tepesch has been as good or better than Perez. And if you break things down even further, Tepesch continues to stack up well against Perez.
According to more data, Tepesch throws more strikes and gets hitters to chase more stuff out of the zone than does Perez.
Of course, Perez's injury is awful for depth. If he was healthy, Tepesch would be replacing Matt Harrison instead. But as far as one for one, the trade-off between Perez and Tepesch might not be as lopsided as we think.
At least that's the hope.