When Bobby Keppel was called up from Rochester on June 24th, the Twins were in need of a reliever that could produce at a sustainable pace. Luis Ayala, the touted "groundball" pitcher, failed to do so and drew the ire of Ron Gardenhire by leaving too many sliders up in the zone. As replacement level-type pitcher getting groundballs at a 51 percent clip in AAA, Keppel would be a suitable and inexpensive gamble to supplant Ayala in the bullpen.
From June 27th to July 19th, Keppel had pitched in seven game, thrown 16 inning while allowing one earned run on just eight hits along with a 0.57 GB/FB rate. The right-hander appeared every bit the answer. Yet after July 19th, Keppel would work in seven more games and allowing 12 earned runs on 17 hits with a nasty 7/2 BB/K ratio. Put simply, Keppel was getting smashed up in the zone, an area he rarely entered in his first seven outings.
Trajectory | Strike Zone Plots
June 27, 2009 versus Cardinals
On June 27th, Gardenhire turned to Keppel to maintain the Twins 5-3 deficit against St Louis to two runs. Keppel pitched admirably, surrendering a leadoff triple to Joe Thurston in his first MLB appearance since 2007, but held the Cardinals scoreless while pitching the fourth through the seventh. True to his form, Keppel got seven of his 11 balls in play to be hit on the ground. Location was Keppel's saving grace. By keeping the ball down in the zone (under the two-foot line on average) and away from the middle of the strike zone, hitters were forced to beat the ball into the dirt. His fastball's velocity was averaging 94.0-mph on that June 27th game as he peppered in a biting slider as well.
June 30th, 2009 versus Royals
His next outing in Kansas City on June 30th was much the same. In his 2 1/3 innings of work, Keppel recorded four groundballs on five in play and struck out three batters. His fastball had slowed a bit (93.5-mph) but he kept it at the knees or lower to avoid heavy contact:
July 28th, 2009 versus White Sox
The All Star break interrupted Keppel's feelgood storyline. When baseball resumed, Keppel struggled mightily as his pitches began to ascend in the zone and his sinking fastball was no longer knee-height (nor was the velocity closer to the mid-90s range). On July 28th, Keppel was summoned to face the Chicago White Sox in the eighth inning. His fastball, now averaging out at 93.2, is not thrown in the lower half of the zone but rather is sneaking up towards the middle of the plate -- an area that is more readily driven across the ballpark.
July 31st, 2009 versus Angels
Following a nine-pitch outing on July 31st against Los Angeles, Keppel returned the following night. With the Angels ahead six-to-four, Gardenhire turned to Keppel following RA Dickey's 2 2/3 inning effort. Keppel rewarded his manager's decision by surrendering back-to-back home runs to Juan Riviera and Kendry Morales. The right-hander would settle in and work 2 2/3 innings himself, allowing the two home runs but would give up six flyballs to his five grounders. On top of that, his fastball's velocity would drop to an average of 91.7-mph - 2.3-mph slower and an additional .013-seconds to the plate.
August 4th, 2009 versus Indians
On Tuesday night in Cleveland, with the Twins cruising to a 10-0 victory, Keppel was given the task of escorting Scott Baker's shut-out through the ninth inning. Although his velocity returned (93-mph plus on average), Keppel labored to keep the ball down. Jhonny Peralta doubled followed by a Travis Hafner single to end the scoreless drought. Both pitches were up in the strike zone.
The natural inclination when something is wrong with location is to instinctually look at the release points and see if something has changed. According to his release plots - arranged oldest to newest - we see that his point of release has shifted above six feet in height. This is an indication that his arm is straighter upon release and potentially causing less downward movement as a result. The alteration could be related to Keppel attempting to aim the pitches rather than throw with his fluid motion but another hypothesis could envolved this being a product of arm fatigue. After all, his velocity changed significantly between outings.