What's Wrong with Boof?
Not too long ago, Bonser was one of the pitching crown jewels of the Twins organization, blasting through double-A and triple-A ball after being acquired in the AJ Pierzynski trade with San Francisco. In 2005 with the Rochester Red Wings, Bonser racked up 168 strike outs in 160.1 innings (24.5% k%) finishing 11-9 with a 3.99 era. The following season, Bonser began back in triple-A and was producing similarly - 83 strikeouts in 86 innings pitched (22.9%) – when in late May the Twins desperately needed his help. In his debut in Milwaukee gave Twins fans a glimpse of the last of the Pierzynski dividends as Bonser finished six innings while striking out 8 and surrendering just the one run. His subsequent starts were less successful as in his next six starts Bonser tossed 29.2 innings only to have a 6.07 era in that duration with opponents hitting .299/.354/.556 off of him. From August on, Bonser pitched significantly better, starting 11 games and throwing 64.2 innings with a 3.62 era. This end of the year performance earned him the Game 2 start in the ALDS against the Oakland Athletics. Esteban Loaiza and Bonser matched each other with two runs a piece. The Twins bullpen conceded three more runs after Bonser left the game and the offense could generate anything against the Oakland relievers.
As Twins long-time rotation fixture Brad Radke retired after the 2006 season, a lot of attention was placed on Bonser hoping that he could stabilize the Twins rotation with his 19 starts of experience. With high hopes in 2007, Bonser failed to live up to vaunted expectations, finishing the season with 8-12 in 30 starts with a 5.10 era (4.98 fip) and an eventual demotion to the bullpen. The had gone 14 and 17 in his starts a big disappointment from management and the front office who were hoping that Bonser would improve on his 10-8 appearance record in 2006. This performance set off a whirlwind offseason in which Bonser was determined to loss weight, attributing the disappointing season to being overweight. "I know last year was a wake up call for him," Gardenhire
said this past spring. "We took him out of the rotation, and I think he was pretty disappointed. I expected that and hoped for that. I think it kind of lit a fire under him, hopefully."
In his first six starts of the 2008 season, Bonser performed much better than his 2-4 record reflects. In 36 innings Bonser struck out 22 and walked just 9. Opponents were hitting just .250/.293/.379 off of him. In his final six starts of the season (so far) Bonser had tossed 30.1 innings and had struck out 20 and walked 11. Opponents increased their batting line to .286/.340/.459 in that time capping it off with an 8.60 era. "I want to be in the starting rotation,'' Bonser told the press after getting shellacked by the New York Yankees on May 30th, on what would be his last start to date, "I know guys are pitching better than me. Whatever their decision is, is their decision. It's just unfortunate that I had such a bad month. I would like to say that, hopefully, this [outing] would be a game to turn me around and get things rolling. It just stinks to be at this point and not getting production I know I can do.''
For the record, Bonser had not been all bad. His 4.09 fip is an indication that he is throwing much better than his 6.48 era would suggest. This is his lowest FIP to date at the major league level. As a starter he was only being supported with 3.65 runs per start. Since his second demotion to the bullpen in as many seasons, Bonser has made six appearances and has given up runs in all but one of those outings. As a reliever, Bonser has contributed an 10.38 era as opponents were smashing him with a .452/.489/.571 batting line. "I was throwing strikes; that's what's weird," Bonser told the Pioneer Press after the May 24th outing in Detroit in which he gave up 8 earned runs in 3 innings of work and allowed Magglio Ordonez to crush a home run that cleared the Tigers bullpen. "I was throwing off-speed pitches, and they weren't getting fooled."
| 2007 | Usage% | Speed | WHIFF | BABIP |
| 2008 | Usage% | Speed | WHIFF | BABIP |
| Fastball | 54% | 91.9 | .071 | .408 | Fastball | 58% | 90.7 | .118 | .289 | |
| Curve | 19% | 79.5 | .247 | .389 | Curve | 15% | 79.1 | .323 | .353 | |
| Slider | 20% | 85.6 | .204 | .324 | Slider | 17% | 85.9 | .172 | .356 | |
| Change | 6% | 82.2 | .068 | .294 | Change | 6% | 82.7 | .194 | .429 |
The first reason for Bonser’s 2008 decline is his self-diagnosed off-speed pitches: batters are just not getting fooled as he mentioned in May. According to pitch f/x data supplied by Josh Kalk seminal website From Small Ball to the Long Ball, we can analyze and visually see in the chart above that Bonser is indeed having some issues with his breaking stuff. In 2007, Bonser alternated between his curveball, which he preferred for left-handed batters (23% of the time), and slider, his right-handed batter’s weapon of choice (31% of the time), to off-set his fastball. His 91.9-mph average fastball, one that sinks (~90) and one that was straight (~93), was hit hard. Opponents swung and missed on the fastball just 7.1% of the time (as indicated by his .071 WHIFF average) and had a hefty .408 average on balls in play. His curveball proved to be the most effective pitch in his repertoire as it had a .247 WHIFF average. The slider wasn’t far behind with a .204 WHIFF average. Both the curveball and the slider, two pitches very capable of inducing a strikeout, also had high averages when put into play.
Lefties absolutely mashed Bonser in 2007. In 411 plate appearances, left-handed opponents hit .349/.407/.563 though he struck out his fair share of them as well (17.7% k% vs lhb) more so than right-handed batters (17.4% k%). This is evident because Bonser relied strictly on his fastball (58%) and curveball (23%) two pitches that were extremely hittable (the fastball more so) but he also was able to strike out that many because his curveball had the highest WHIFF average AND called strike average (32%). The righties, however, had a more difficult time scratching out hits off of Bonser. In 361 plate appearances the right-side opponents managed just a .214/.285/.360 batting line. Bonser had been feeding them steady diets of fastballs (49%) and sliders (31%) with greater results than the left-handed counterparts, mostly because his slider was less likely to succumb to a base hit when put into play.
His approach to hitters shifted somewhat in 2008 in terms of pitch distribution. Left-handed batters are now seeing more fastballs (64%) while Bonser hasn't used one particular offspeed pitch to the group. Seeing as that his swing-and-miss rate had improved on his fastball (.118 vs. .071) and that the contact made was creating more outs (.289 vs .408) the reliance on the fastball was the reason left-handed opponent average declined to .297/.322/.441. Right-handed batters on the other hand still saw the same dosage of fastballs (53%) and sliders (23%) only now Bonser has begun tossing the curve at them as well (17%). This has resulted in an increased opponents batting line from the low .214/.285/.360 in 2007 to a hefty .288/.322/.441 in 2008. One possible explanation for this is that his slider has flattened out. What was his second most dominating pitch last year is now arguably his least successful one. The WHIFF average has decreased to .172 and opponents are hitting .356 when they put the ball in play.
The second reason is due to one of Bonser’s 2008 resolutions. The first of which we have all seen was him shedding 25 pounds to increase the yet-to-be-seen endurance. The other, more subtle resolution was to use his change-up more frequently. "Last year, I threw like maybe one or two a game,'' Bonser said discussing his 2007 usage of the change, "and that was amazing." So far Bonser has interspersed his change-up along with his other off-speed weapons into the game with as much frequency as he did last year (6%) only this time the results are significantly different. Last season Bonser had fewer swings-and-misses with his change-up (.068 WHIFF) than his fastball (.070 WHIFF) but saw the pitch be the hardest pitch to reach base with (.294 babip). This season he has been able to get more bats to miss (.194 WHIFF) with the pitch but only to find it very hittable (.429 babip).
What is reassuring is that Bonser's fastball is solid. Not only because of the velocity and the lack of hits produced by it, but also Bonser's control of the pitch. Last season Bonser threw his fastball in the zone 63% of the time and this year he has been around the plate 70% of the time. Like Scott Baker, Boof Bonser should take a lesson and rely on his two best pitches and disperse a third to change a hitter's eye line. Baker is a two trick pony using the fastball liberally (63%) and following that with his slider (21%). On occasion, Baker tosses in a good curve (10%). Bonser, as he is trying to regain his form in the bullpen, should begin by eliminating the change for the time being. True Bonser has only thrown it approximately once an inning, but when you consider that this pitch is detrimental when put into play, the idea of forcing it in for having a "fourth pitch" is not helping. Even throwing this pitch once an inning creates the possibility of continuation of said inning, more so than any other of his pitches. 42% of the time a batter makes contact with it that batter reaches base safely, prolonging the inning. In 16 different innings this year Bonser has thrown 20 or more pitches. Furthermore, his change's rate of speed (82.7) only varies it from his slider by 3 miles per hour on average - the pitch must appear to be a hanging slider to the batter - Bonser could easily obtain the same effect with his curveball which has a 6.8 mile per hour difference plus has a greater WHIFF average. The second measure he should take is to downshift the usage of the slider. I am not suggesting the pitch be discarded but rather take a back seat to his existing fastball (sinker/two seamer) and curveball. Instead of combating right-handed batters with a pitch that has been hit far too often, Bonser needs to concentrate once again on throwing his curveball, one that has a .323 WHIFF average.
