Brian Matusz entered the 2010 season considered one of the top rookie pitchers in the game. Marc Hulet of Fangraphs recently wrote that he thinks Matusz will win the AL Rookie of the Year. Things haven’t been so rosy for the Baltimore lefty in the last month, however.
Matusz hasn’t pitched excellently in 2010 according to his peripherals. He’s better than his 5.8 ERA, but he’s worse than 3.8 FIP on account of an unsustainable 6.2% HR/FB. His xFIP of 4.6 looks a lot more like the pitcher that he is. He’s striking out a lot of hitters (7.4 per 9), but his fly-ball tendencies are extreme (46.5% over 446 batters faced) and his control looks spotty: 3.3 BB/9 this season.
It’s the last part I want to take a look at, because a (career) 3.1BB/9 is going to wreck a fly-ball pitcher like Matusz unless he can develop swing-and-miss stuff that will get him a strike out per inning. But here’s the thing: Matusz control has been impeccable through his major league career.
54.3% of his pitches have hit the zone since he first took the mound in 2009. For comparison’s sake, just four pitchers managed to throw that percentage of pitches (or more) in the zone last season: Ted Lilly, Cliff Lee, Johan Santana and Roy Oswalt (who tied Matusz’s 54.3%). Just below that are Justin Verlander and Scott Baker. Matusz has allowed 7.6% of hitters a free pass since his arrival. Of those six comparisons, the highest walk percentage was 6.5% (Santana), the lowest 4.4% (Lee) and the average was 5.6%. Somehow Brian Matusz manages to walk 35% more batters than the average of this group of similar pitchers.
It gets even stranger. Matusz throws pitches in the zone, but he’s not exactly a pitch-to-contact guy. His contact rate on pitches in the zone (=83.3%) is about 4% below major league average (~=88%). He does tend to allow contact on pitches out of the zone, but the net result is an average contact rate, and his swinging strike rate of 9.3% is 1% better than the major league average. He’s not throwing pitches in the zone because he gets behind in the count: his 62.0% F-strike rate place him around the top 15% of starters with 60 or more IP last season.
If we adjust his walk rate to reflect what pitchers with a similar rate of pitches in the zone do, Matusz would have just 15 walks this season and a 3.0K/BB ratio. That’s good enough to produce a 4.2 xFIP and 3.6 FIP. ( I calculated the expected walk rate at 6% of batters faced. I calculate expected HR for xFIP as 6.5% of line drives plus flyballs, i.e., balls in the air, rather than as proportion of fly balls to account for inconsistencies in LD and FB scoring.)
While it’s difficult to tell a lot about a pitcher from his plate discipline stats, two things do stand out: swinging strikes get Ks and pitches in the zone prevent walks. The correlation coefficent between BB/BFP and zone% was -.43 for 78 qualified starting pitchers in 2009, which is a pretty strong correlation for baseball.
It would be really cool if I had an explanation of Brian Matusz high walk rate, but it confounds me, and I’m completely open to suggestions. His walks look like an anomaly.