Is Jake Westbrook the Indians' best starter?

Indians righty Jake Westbrook is an interesting case study in how much luck factors into a pitcher’s season. For all practical purposes, Westbrook’s 2004 and 2005 lines were identical. Westbrook faced the exact same amount of batters each season, gave up the exact same amount of homers, walked three less in 2005 and struck out five more. That’s as identical as two seasons can be. Yet his 2004 ERA was 3.38, while his 2005 ERA was 4.49. He gave up a ton of groundballs each season. Even his batting average per ball in play (BABIP)---much of which is out of the pitcher’s control---was very similar (.276 in 2004 versus .290 in 2005). What did Jake do differently?

For all intensive purposes, Jake himself did nothing differently. His “skills” (homers, walks, strikeouts) were exactly the same. Let’s look further at some of the factors that Jake cannot control.

**Defense: The Indians ranked third in baseball in defensive efficiency. Ronnie Belliard and Jhonny Peralta were among the best at their positions defensively, and Aaron Boone was above average. Ben Broussard was merely average. Overall, the Indians were excellent defensively, especially on the infield. Thus, Westbrook’s higher BABIP is strange.

**Line Drive Percentage: Westbrook ranked 11^th out of 44 qualifying AL starters in lowest line drive percentage (line drives tend to fall for hits more often than regular batted balls). Hitters do not often hit line drives off of Westbrook; this furthers the idea that Westbrook’s amount of hits given up in 2005 is abnormally high.

**Homers per fly ball: Westbrook was the worst of the 44 qualifying AL starters in homer per fly ball ratio (this ratio is park adjusted). 19% of the fly balls that Westbrook allowed (and remember, Jake allowed the fewest fly balls per ground ball of any pitcher in the AL) became homers. This is an extremely high percentage---research has shown that pitchers average an 11% HR/FB ratio, and any deviation is mostly attributable to luck.

**Left-on-base percentage: Westbrook was third worst in LOB%, which measures the percentage of base runners who come around to score. A mere 62.9% of Westbrook’s base runners failed to score (for comparison, both Cliff Lee and Scott Elarton stranded 72% of their base runners, while Kevin Millwood ranked 2^nd in the AL, stranding 79% of his runners).

All of these factors played a large role in Westbrook’s higher 2005 ERA. If we delve even further into Westbrook’s stats, we see that he was the anti-Kevin Millwood in terms of “clutch pitching.” Overall, opposing batters hit .265 against Westbrook. However, with runners on base, batters hit .298 against him. Furthermore, although Westbrook had 130 fewer at-bats against him with runners on base, Westbrook allowed 11 of his 19 homers to occur when runners were on base. With runners in scoring position, batters hit .304 against him. With a runner at third base, the opposition hit an absurd .542. Opposing batters hit .360 with runners at first and third, .353 with the bases loaded, and a crippling .333 with runners in scoring position and two outs. In 2004, opposing batters hit .255 overall against Westbrook, but a mere .233 with runners in scoring position and .200 with runners in scoring position and two outs.

Westbrook is just now entering his prime. We can reasonably expect similar IP, BB, and K in 2006. However, we can also expect less home runs, less hits, and less of the runners who do get on base scoring. These are three very important factors that influence ERA, and Westbrook got very unlucky in all three facets in 2005. Furthermore, we can expect a regression to the mean in terms of batting average in clutch situations as well as the amount of homers that occur with runners on base. Thus, although a return to the 3.38 ERA of 2004 is unlikely, Westbrook has a very good chance of bettering his 2005 ERA, perhaps by a fair amount.