Jered Weaver’s K Rate

Though the Los Angeles Angels of Anaheim have played .500 ball to this point and have a run differential (negative 26) that suggests they’ve been lucky to break even, you can’t blame Jered Weaver. The 27-year-old righty, selected out of Long Beach State with the 12th pick in the 2004 draft, is turning in the best season of his major league career.

In 75.2 innings pitched, Weaver boasts a 3.40 expected FIP (xFIP) that places him sixth in the American League among starters tossing at least 50 frames. Weaver is displaying customarily sharp control, issuing 2.5 free passes per nine innings and getting ahead in the count with a 60.1 first pitch strike percentage (58% MLB average). But the biggest reason for his lights-out pitching is a large increase in whiffs.

Weaver is getting swinging strikes 11.3% of the time in 2010, well above his career 9.4% mark and the 8-9% big league average. His overall contact rate is 75.1%, besting his 78.8% career clip and the 80-81% MLB average. On a related note, Weaver is getting hitters to expand their zones more often, with a 31.6 Outside Swing% (27.3% career average, 25-27% MLB average in recent years).

Consequently, Weaver’s K rate has climbed:

Heading into 2010, Weaver had 7.32 K/9 during his career. CHONE predicted 7.25 K/9 for him this year, and ZiPS 7.1 K/9. After an eight punch out performance against the Royals yesterday, Weaver now has 9.87 K/9 on the season. That’s second among AL starters, behind only Toronto’s Brandon Morrow. But Weaver has actually K’d more on a per-plate appearance basis: Jered has a 27.1 K%/PA, compared to 26.1% for the control-challenged Morrow (those extra free passes extend the inning and give him more chances to whiff batters).

So, is Weaver doing anything different this year? Here’s his pitch selection over the 2009 and 2010 seasons (data from Trip Somers’ texasleaguers site):

Jered’s four-seamer is a tick quicker, and his whiff rate with the pitch has gone from below the six percent big league average to a robust 9.3%. He has added a two-seamer to his repertoire, which may help explain his (relative) rise in ground balls (37.8 GB%, compared to a career 32.9 GB%). The whiff rate on his slider has increased considerably (from 12.2% to 17.3%), though his curve’s rate of whiffs has declined (12.7% in ’09 and 9.3% this year).

Weaver hasn’t thrown his changeup as much this season, but when he does, he’s still getting a ton of swings and whiffs. The relative difference in velocity between his four-seam fastball and change has increased — there was an 8.3 MPH gap in ’09, but an 11.6 MPH split in 2010.

There’s also a change in terms of the relationship of horizontal movement between the two pitches. In 2009, Weaver’s four-seamer had 3.3 inches of movement in on the hands of right-handed batters, while his change had 5.7 inches of movement away from lefty batters (a 2.4 inch difference). In 2010, Weaver’s four-seamer has 1.4 inches of horizontal movement, and his change has 6.8 inches (5.4 inch difference). For reference, the average difference in horizontal movement between four-seamers and changeups (per Somers’ site) is about half an inch.

Perhaps that big gap in movement, coupled with the introduction of the two-seamer (which has similar horizontal movement as the change), is flummoxing hitters. According to our Pitch Type Run Values, Weaver’s fastball/change combo is faring better than ever: his fastball has been worth +0.64 runs per 100 pitches thrown (+0.07 runs/100 career) and his changeup has been +2.79 per 100 tosses (+1.38 career).

Is Weaver’s increased K rate to be believed? To an extent. Strikeout rate per plate appearance for pitchers tends to become reliable around 150 batters faced, and Weaver has taken on 306 hitters so far this season.

The change is Weaver’s whiffs is reflected in his rest-of-season ZiPS projection — the ROS ZiPS are so helpful because they incorporate a player’s performance during the current season, giving us a more accurate reflection of his talents. ZiPS projects Weaver for about 7.8 K/9 for the rest of 2010, compared to the system’s 7.1 K/9 pre-season forecast. While Weaver isn’t likely to keep whiffing well over a batter per inning, his increase in K’s should not be written off as a total fluke. Odds are, he’ll keep some of the gains that he has made.