Johan Santana’s Strikeouts

Johan Santana’s career credentials are unquestioned. The Venezuelan southpaw, a Rule V gem who won two Cy Young Awards with the Twins, has a 3.39 FIP in the majors. He’s got over a K per inning during his career, and he topped the seven WAR mark each season from 2004-2006. Santana was “merely” a four-to-five win pitcher in 2007-2008, before elbow surgery to remove bone chips ended his ’09 season early and caused him to post 2.8 WAR.

On the surface, the 31-year-old’s 2010 season looks like vintage Santana — in 78.1 innings, he’s got a 2.76 ERA. But the process behind those results isn’t as impressive.

While the Queens version of Santana in ’08 and ’09 didn’t miss bats at the same rate as his halcyon days with the Twins, he still managed swinging strike rates in excess of 11 percent (8-9% MLB average) with an overall contact rate in the 77-78% range (80-81% MLB average). This season, Santana is getting swinging strikes 9.4%, with a contact rate right around the big league average.

As a result, Santana’s strikeout rate has declined — from 7.9 batters per nine innings in ’08 and ’09 to 6.55 K/9 in 2010. His walk rate has climbed somewhat as well (2.76 BB/9, from the 2.4-2.5 BB/9 range the previous two years), though not alarmingly so. Santana’s expected FIP (xFIP), derived from a pitcher’s K’s, walks and a normalized home run per fly ball rate, is 4.48.

Now, that mark likely exaggerates the extent of Johan’s struggles. His BABIP is pretty low at .268, but Santana has generally posted lower-than average BABIP figures (.286 career). Santana gets a lot of fly balls (35.8 GB% in 2010, 37.8 GB% career), which have a lower BABIP than grounders. He induces a lot of weakly hit pop ups, with a 12.7% infield fly rate this year and a 13.2% mark for his career. Santana’s rate of stranding base runners (79.7%) is well above the 70-72% MLB average, but his career rate is 77.5%. It seems reasonable to suggest he’ll continue to have a LOB rate above the big league norm. Santana’s home run per fly ball rate (5.5%) almost assuredly will rise, though.

So, Santana hasn’t performed near as well as his ERA suggests, but probably not as poorly as his xFIP indicates. His falling K rate is worth examining further, however. The velocity on Santana’s four-seam fastball has declined again this season, as has the zip on his slider. But those aren’t the root causes for the reduced number of whiffs. Take a look at Santana’s whiff percentage by pitch over the 2008-2010 seasons (data from Trip Somers’ texasleaguers site):

Perhaps as a result of hitters not anticipating it as much, Santana has actually gotten a higher whiff rate on his four-seamer. His two-seamer has a very low whiff percentage in 2010 after getting an above average number last season. That most glaring difference, however, is the whiff rate on the changeup. Santana’s signature change got a whiff 22.4% in ’08 and 17.4% in ’09, but just 13.6% this season (12.1% MLB average). That’s a substantial drop.

Though his ERA is pristine, Johan Santana really isn’t in the conversation anymore when it comes to the absolute best starters in the game. That doesn’t mean he’s done being a quality pitcher, but he’s not fooling hitters with the same regularity these days.