Bobby Jenks: Finesse Pitcher?

As a member of the Angels organization, right-hander Bobby Jenks was something of a mythological figure. The gargantuan 6-3, 280 pounder, selected in the 5th round of the 2000 amateur draft, often had radar guns begging for mercy as he sat in the upper-90’s and hit triple-digits on occasion. With that hopping heater, Jenks mauled minor league hitters (9.4 K/9), but his control (an astounding 6.01 BB/9) and temperament left much to be desired.

Despite Jenks’ gifts, the Angels eventually grew tired of the flame-thrower’s antics and punted him off the 40-man roster in December of 2004. The White Sox stepped up and claimed the volatile-but-talented arm, and the club has been rewarded handsomely for its leap of faith.

Jenks burst onto the scene during Chicago’s World Series run in 2005, punching out 11.44 batters per nine innings in 39.1 frames. His control (3.43 BB/9) was just fair, but he managed a 2.69 FIP while showing off a 97 MPH fastball as well as two hard breaking balls (an 88 MPH slider and an 83.5 MPH curve).

The portly righty displayed many of the same attributes in 2006. In 69.2 innings, Jenks used a slightly-less searing 95.8 MPH heater and his hard breaking stuff to post rates of 10.33 K/9 and 4.0 BB/9. Despite the occasional bouts of wildness, Jenks used his ability to miss bats and a newfound tendency to keep the ball on the ground (his GB% improved from 44.6% in ’05 to 58.8% in ’06) to compile a 3.20 FIP.

After two seasons of dominating hitters and allowing a few too many free passes, Jenks performed like a different sort of hurler in 2007. His K rate fell precipitously, from over 10 K/9 down to 7.75. However, he cut his walk rate by more than half (1.8 BB/9) and continued to burn worms (53.8 GB%). Jenks’ blistering upper-90’s cheese was now sitting in the 94 MPH range. The shape of his production was different, but Jenks posted the best K/BB ratio (4.31) and FIP (2.56) of his career.

2008 continued Bobby’s trend of missing fewer bats. A few short years after posting a double-digit whiff rate, Jenks struck out just 5.55 batters per nine innings, while walking 2.48 per nine. His groundball rate (57.6%) remained quite high and his FIP was still a fair 3.41, but clearly the present version of Jenks is not the same fire-breathing mountain man that was on display in Los Angeles’ farm system or in Chicago during his early days there. Jenks was once fairly difficult to make contact with, but opposing hitters have progressively had an easier time putting the bat on the ball:

Jenks’ Contact Rate, 2005-2008:
2005: 74.5%
2006: 77.8%
2007: 79.1%
2008: 84.5%

Jenks’ 2008 contact rate was one of the highest among all relievers. Residing close to Bobby were names such as Ryan Franklin, Brian Bass and Franquelis Osoria.

Bobby Jenks’ transformation from flame-throwing folklore to finesse pitching has been fascinating to watch. Chicago’s plus-sized closer has remained effective to this point (his 3.47 WPA in ’08 was a career-best), but it would probably be best to tread cautiously here instead of investing a high pick. Jenks could well remain effective with plus control and groundball tendencies, but his descending strikeout rate and back issues bear watching.