Replacing Martin Perez with Martin Perez

The Rangers, already the most injury plagued team in baseball, got a double dose of bad news on Wednesday.

Matt Harrison’s lingering back problems have simply not abated, and now he’s looking at either trying to pitch through serious pain or face a spinal fusion surgery which could potentially threaten his Major League career. Meanwhile, Martin Perez — who lasted just 3 2/3 innings on Saturday — was diagnosed with a tear in his UCL, and is probably going to join the Tommy John parade. The Rangers were already trying to get by without Derek Holland, Jurickson Profar, and Geovany Soto, as well as a host of role players who had been pushed into larger roles due to the team’s injury epidemic.

With both Perez and Harrison potentially out for the season, the Rangers rotation is in shambles, and some national pundits are already writing the team’s obituary. And certainly, losing 40% of your rotation on one day is not going to improve your team’s chances of making the playoffs. The Rangers are worse today than they were yesterday. But let’s keep some perspective; few players are so good that their loss would dramatically the needle for a team’s playoff odds, and the Rangers replacement for Martin Perez might actually be just as good.

Nick Tepesch has never been a highly regarded prospect. He was a 14th round pick in the 2010 draft. Baseball America never rated him higher than the 19th best prospect in the Rangers organization, and Marc Hulet has never mentioned him in any of his off-season rankings of Texas’ farm system. He’s been seen as just a guy, an organizational arm of limited upside. Perez, meanwhile, has rated as highly as the #17 prospect in baseball per BA, and has been on the Top 100 five times.

But let’s put aside our expectations for a second, and compare what they’ve actually done in the big leagues. Here are their career numbers as Major Leaguers.

Martin Perez 213.2 8% 16% 49% 10% 72% 0.306 97 97 103 3.0 2.9
Nick Tepesch 98.1 7% 20% 47% 13% 70% 0.305 110 97 95 1.4 0.8

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.

Name O-Swing% Z-Swing% Swing% O-Contact% Z-Contact% Contact% Zone%
Martin Perez 29% 64% 45% 65% 90% 81% 46%
Nick Tepesch 32% 63% 47% 63% 91% 81% 48%

Despite the scouting community’s overwhelming preference for Perez’s stuff, Tepesch has thrown more pitches in the strike zone while simultaneously getting hitters to chase more of his pitches out of the zone, and hitters have posted a lower contact rate on pitches out of the zone against Tepesch than they have against Perez. Overall, these two lines are very similar, but where there are differences, they actually favor Tepesch.

But, of course, we’re only dealing with 87 big league innings for Tepesch, while Perez has thrown over 200. Given two similar performances, it’s entirely reasonable to prefer the one that came over the larger sample. But even if we stretch the comparison back to Triple-A, Tepesch continues to hold his own.

In seven starts down in the PCL this year, Tepesch posted a 41/9 K/BB ratio over 46 innings, compiling a 1.58 ERA/2.90 FIP, which rank 2nd and 4th respectively among pitchers with at least 40 innings in that league this year. Perez was also quite good in his short stint in the PCL last year, posting a similar walk rate, but striking out a few less batters and posting a FIP of 3.21, a little higher than what Tepesch put up this year.

Taking all of their relevant performance data into account, and adjusting for things like fastball velocity and age, both the ZIPS and Steamer forecasts see Perez and Tepesch as essentially equal pitchers. Here are their rest-of-season projected FIPs, from both systems.

Pitcher ZIPS Steamer
Martin Perez 4.44 4.49
Nick Tepesch 4.45 4.39

Despite the wildly different prospect pedigrees, both forecasting systems look at these two pitchers for 2014 and see basically the same results. In terms of the Rangers chances of reaching the postseason, swapping out Perez for Tepesch barely matters at all. It does take away some of the team’s depth — if Perez hadn’t been hurt, then Tepesch could have stepped in for Matt Harrison — but if we’re evaluating just Perez’s rotation spot now filled by Tepesch, it’s not entirely clear that the Rangers are actually worse off.

This isn’t to say that Perez doesn’t have the brighter future, or at least, that he didn’t have more upside before the UCL tear. Scouting reports do matter, and the fact that scouts universally preferred Perez is useful information. But the entire nature of scouting pitchers can lead to an unhealthy emphasis on things like velocity, which don’t matter as much on the mound as they do in deciding which prospects rank where. And if we’re talking about the effects of Perez’s injury on the Rangers playoff chances, then we don’t really care too much about upside or long-term potential.

Take heart, Rangers fans. Losing Martin Perez isn’t a crippling blow. The A’s aren’t going to be easy to catch, but even their early success after losing Jarrod Parker and A.J. Griffin should be a reminder to not overstate the impact of a couple of injuries to non-star pitchers. Jesse Chavez has proven to be a more than capable replacement, and it shouldn’t surprise us if Tepesch fills Perez’s shoes nicely as well.

Dave is the Managing Editor of FanGraphs.

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9 years ago

A lot of 4seam fastballs averaging 89 MPH yesterday. Overall velocity down a couple MPH. Good 4seam, slider, and curve. If location and movement are good he could be a real asset.