Not long after Boof Bonser's sentence to the bullpen, I analyzed Boof's pitching through the use of pitch f/x. My conclusion at the time was that his slider, a pitch he threw nearly a quarter of the time to righties, was flattening out at that time in the season, resulting in an unexpectedly high .288/.322/.441 batting line against righties as of June 14th. Still, at the conclusion of the season, Bonser had improved his approach against the same-sided opponents, dropping his batting line against to .260/.295/.405, suggesting that he had regained his slider and his repertoire was playing well in the 'pen, a sign that he could be capable of assuming a meatier role in the 2009 bullpen. In addition to this in-season improvement, there are several other statistical indications that -- as the Counting Crows song so eloquently puts it -- this year could be better than the last. For starters, his fielding independent metric of 4.51 was much better than his swollen 5.93 ERA. Secondly, his left-on-base percentage of 57.9% and those with severely low LOB% sometimes rebound the following season. Lastly, Bonser's candidacy as a solid bullpen contributor is buttressed by his minor league legacy. Over the course of seven minor league seasons, Bonser has struck out 916 batters in 884.1 innings while walking just 398. His last full season at AAA in 2005, Bonser led the International League in strikeouts.
It is hard to refute those three cited examples as justifiable reasons for Bonser being anything but an excellent internal candidate for the vacant set-up role. However, if you look closer at his numbers, there are two glaring problems with Bonser's game that supersedes his ability to be an effective reliever in high leverage situations: (1) He is useless against left-handed opponents and (2) He can't pitch from the stretch.
The first is his approach against left-handed opponents.
|
vs LHB |
Bonser |
RHP League-Average vs LHB |
|
2006 |
.251/.305/.451 |
.279/.349/.446 |
|
2007 |
.349/.407/.563 |
.275/.349/.438 |
|
2008 |
.315/.378/.486 |
.269/.346/.430 |
Lefties are a demographic that had not given Bonser trouble in 2006 but were suddenly a blight on his landscape in 2007. In his first year, Bonser had limited lefties to a .251/.305/.451 batting line. In the subsequent season, it swelled to .349/.407/.563. Prior to his demotion to the bullpen, Bonser had improved upon his 2007 numbers with a .297/.322/.441 line. Unfortunately he regressed in the 'pen and at the 2008 season's end, lefties had hit a collective .315/.378/.486. If you are looking for a silver-lining, it was a tad better than his 2007 numbers on the whole, however, the bulk of the destruction happened when Bonser was in relief.
More recently, in 12 starts in 2008, Bonser had thrown 66.1 innings with a 42/20 K/BB and high 7.08 RA but a low .267/.316/.418 opponent batting line. Following his transition to the bullpen, Bonser threw 52 innings and compiled a 55/16 K/BB ratio but still posted a 6.02 RA as opponents batted .307/.353/.474 off of him. As I mentioned above, Bonser's opponent average against right-handers DROPPED when converted to a reliever. On the other hand, up until June 14th lefties were hitting .297/.322/.441. At the end of the season, it rose to to a firm .315/.378/.486. The inflated batting line as a reliever came in direct result of left-handed opponents.
The second problem is that he is atrocious when pitching from the stretch (something that relievers are requested to frequently, often with the game on the line). Similar to his left-handed struggles, pitching with runners on manifested itself after his rookie season.
|
Runner On Base |
Bonser |
League-Average |
|
2006 |
.267/.319/.466 |
.274/.348/.425 |
|
2007 |
.294/.367/.478 |
.277/.350/.430 |
|
2008 |
.322/.349/.467 |
.274/.348/.425 |
What seems to be given him the biggest problem is when runners are on first - more so than any other base path alignment.
|
Runner On First |
Bonser |
League-Average |
|
2006 |
.295/.313/.526 |
.277/.335/.435 |
|
2007 |
.360/.416/.640 |
.284/.342/.442 |
|
2008 |
.369/.411/.500 |
.277/.348/.425 |
In addition to the higher batting line, Bonser's stolen base rate skyrocketed too from 57% SB% in 2006 (4 in 7), 61% in 2007 (11 in 18) and 100% in 2008 (11 of 11). Considering that limiting a baserunner from scoring may be more important in the later innings in a high leverage situation, Bonser appears to be a liability under these circumstances. Clearly this is a bigger problem than his weight. This is a mental issue.
