Projecting the Newest Member of the Astros’ Rotation

Don’t feel bad if you somehow missed Joe Musgrove getting called up to the Astros this past Monday. After all, only like a billion other transactions took place that day, many of which involved established big leaguers and/or prospects more highly touted than Musgrove. But now that the deadline-related madness has come and gone, I’d like to direct your attention to Mr. Musgrove. He’ll be joining the Astros’ rotation this Sunday in place of the injured Lance McCullers, and there’s reason to think he’ll be a very good pitcher.

Two years ago, Musgrove wasn’t on anyone’s prospect radar. Though he was drafted way back in 2011, it took him until 2014 to make it out of Rookie ball — and until 2015 to make it into the full-season levels. But when finally given the opportunity to last year, he broke out in a big way. He shot from Low-A to Double-A, putting up a dazzling 1.88 ERA in just over 100 innings. Perhaps even more impressive were his strikeout and walk numbers: he struck out 99, while walking only eight, giving him rates of 25% and 2%, respectively.

Musgrove has effectively replicated those absurd strikeout and walk numbers in 2016. In 85 innings between Double-A and Triple-A this year, he’s struck out 26% of opposing batters, while walking just 3%. You hardly ever see a pitching prospect with a walk rate that low, and you almost never see one who pairs it with a strikeout rate up over 25%. On the downside, Musgrove had a little bit of trouble keeping the ball in the park in his 10 Triple-A starts, but those starts also took place in the PCL, where lots of pitchers have trouble keeping the ball in the park.

My KATOH projection system is very much buying into Musgrove’s performance. It projects him for 5.5 WAR over his first six seasons by the traditional method and 7.2 WAR by the method that integrates Baseball America’s rankings. Those projections place him 46th overall and 28th overall, respectively, on KATOH’s list. Among pitchers, he was eighth and sixth. KATOH’s lists tend to be relatively hitter-heavy — likely due to some combination of pitchers’ attrition rates and the fact that KATOH does not directly quantify “stuff.” But among pitching prospects, my system thinks Musgrove is one of the best out there.

To help you visualize what his KATOH projection entails, here is a probability density function showing KATOH+’s projected distribution of outcomes for Musgrove’s first six seasons in the major leagues.

To put some faces to Musgrove’s statistical profile, let’s generate some statistical comps for the 6-foot-5 righty. I calculated a Mahalanobis distance between Musgrove’s Double-A and Triple-A performance this year and every season at those levels since 1991 in which a pitcher recorded at least 350 batters faced. In the table below, you’ll find the 10 most similar seasons, ranked from most to least similar. The WAR totals refer to each player’s first six seasons in the major leagues. A lower “Mah Dist” reading indicates a closer comp.

Please note that the Mahalanobis analysis is separate from KATOH. KATOH relies on macro-level trends, rather than comps. The fates of a few statistically similar players shouldn’t be used to draw sweeping conclusions about a prospect’s future. For this reason, I recommend using a player’s KATOH forecast to assess his future potential. The comps give us some interesting names that sometimes feel spot-on, but they’re mostly just there for fun.

Though Sunday will be Musgrove’s first big-league start, it won’t be his debut. He already pitched in relief in Tuesday night’s game against the Blue Jays — the team that drafted him — and absolutely dominated. He tossed 4.1 scoreless innings and, in typical Musgrove fashion, struck out eight and only walked one. He also tied the major-league record for most strikeouts as a reliever in his debut. That particular distinction is probably trivial, but whatever: the point is that Joe Musgrove was really good.

Musgrove doesn’t exactly have blow-you-away stuff — he averaged 92 mph with his fastball out of the bullpen on Tuesday — but instead gets by with plus command. With prospects like that, we often don’t see them coming until they’re basically here. They don’t light up the radar gun at the lower levels, and therefore don’t start creeping onto prospect lists until they’ve proven themselves at the upper levels. Musgrove falls into this category as well, as many outlets left him off of their preseason top-100 lists completely. But regardless of his prospect pedigree, Musgrove has made it clear over the last two seasons that he’s very capable of getting minor-league hitters out by way of excellent strikeout-walk differentials. Don’t be surprised if he starts doing the same out of Houston’s rotation.