Jake Peavy: Buy or Sell?

Jake Peavy is back. After scuffling for nearly three season with the Chicago White Sox, it looks like Peavy may have finally returned to form. His performance has been so impressive that Peavy currently leads all pitchers in WAR. Because of his recent struggles, Peavy was likely a late-round pick in most fantasy leagues this season. Now that he’s completely outperformed his draft slot, Peavy could be a popular trade block candidate in many leagues. While Peavy comes with some uncertainty, his early season performance has been encouraging.

Peavy has been a popular candidate at RotoGraphs thus far, as both Dan Wade and Mike Podhorzer have covered aspects of Peavy’s resurgence. As Podhorzer noted, Peavy has been throwing with increased velocity this season. Whether or not that velocity is helping depends where you look. According to pitch type values — which is provided to FanGraphs by Baseball Info Solutions (BIS) — Peavy’s four-seamer has been more effective this season. It’s still incredibly early, but Peavy’s wFB/C is currently 1.31, making it his best performance since his trade to the White Sox. When you look at the Pitch f/x pitch type data — which is provided to FanGraphs straight from Gameday — Peavy’s four-seam fastball has a slightly negative value.

The Pitch f/x data, however, has Peavy throwing a pitch that is categorized differently by both systems. According to the Pitch f/x data, Peavy has thrown a two-seam fastball since 2009, but the BIS data seems to be categorizing it as a regular four-seam fastball. The BIS data also has Peavy throwing 22.4% of pitches as “unknown” this season, and it may turn out that a large portion of those pitchers will end up listed as two-seamers as the season progresses. The two systems may disagree on what he’s throwing, but both agree that some version of his fastball has been better. The Pitch f/x data rates Peavy’s two-seamer at 5.6 this year, making it easily his best pitch.

As a result of his velocity change, Peavy has been able to increase his swinging strike rate to 10.4%, which matches his total from 2008. His K% has also been impacted, increasing from 20.2 to 24.1 this year. While his strikeout rate may not increase dramatically, Peavy may experience a slight boost this year.

While those are extremely encouraging signs, there is also some reason for concern with Peavy. His 78.1 LOB% is unsustainable. Over his career, he’s performed pretty well in the category, stranding 75.6% of runners, but he hasn’t shown that skill since he joined the White Sox. There’s also a significant concern with Peavy’s ground-ball rate. At 24.5%, it’s the lowest in the league and a sure bet to regress. That fact that Peavy plays in US Cellular Field, which is known for being a generous home run park, will ensure his current 1.8 HR/FB rate will increase as well. Even though those things will even out, Peavy still performs incredibly well in FIP (2.02) and xFIP (3.70) this season. Once the home run rate stabilizes, Peavy’s ERA should start to match up with his xFIP.

That’s still a really great fantasy pitcher. And based on his numbers so far, it looks like Peavy has returned. You can’t mention Peavy, however, without talking about his injury history. In mid-2010, Peavy suffered a rare latissimus dorsi injury, in which the tendon completely detached itself from Peavy’s bone. The injury was so rare, that it was actually the first of it’s kind. As much as we can speculate on what Peavy’s increased velocity means about his health, we’re really in uncharted territory here.

Because of that uncertainty, Peavy is a risky bet going forward. He managed to pitch 111.2 innings in his first year off the experimental surgery, so perhaps that is the best benchmark for him this year. If that’s the case, it could be worth holding on to Peavy a bit longer and letting him continue to produce for your team. But around the time he begins to reach those limits, he should probably be a strong trade candidate. There’s always a chance that Peavy continues to dominate, and goes on to have his best year since he was in the National League, but at that point, owners will have sold him way above his draft price. If you’re a Jake Peavy owner, things are looking really good right now.