Duensing was made for the bullpen

While the Twins try to piecemeal together their once glorious bullpen that has now been blown to smithereens, there is one player already on the roster who should help make the late innings much less of an adventure.

As the Star Tribune’s Joe Christensen reported that the team is bumping Brian Duensing from the rotation and relocating him back to the bullpen.

If you separate out the data from Duensing’s match-ups against same-sided opponents, you would see a pitcher with a tremendous track record:

Duensing vs Left-Handed Hitters (2009-11)
	PAs	K%	BB%	GB%	Swg. Str%
2009	90	21.1%	6.7%	60%	24%
2010	153	22.2%	4.6%	53%	28%
2011	187	20.3%	3.2%	55%	23%

(via Fangraphs & Inside Edge)

Last season, Duensing held lefties to a .210 batting average against, the 14^th-lowest among qualified MLB starters last year. What’s more is that Inside Edge’s video scouts found that lefties had a .103 well-hit average off of him – the best in baseball - meaning that nobody on the left was able to put good wood on the ball.

He absolutely stunned them with his outstanding slider. Against his slider, they had a .036 well-hit average (fourth best in baseball) and routinely beat the ball into the ground (61%) for an easy conversion to an out.

Meanwhile, his peripheral stat line against right-handed opponents paints the picture of a much more ordinary and pedestrian hurler:

Duensing vs Right-Handed Hitters (2009-11)
	PAs	K%	BB%	GB%	Swg. Str%
2009	269	12.6%	9.3%	44%	17%
2010	382	11.5%	7.3%	52%	14%
2011	524	14.7%	8.8%	41%	18%

(via Fangraphs & Inside Edge)

Of course, we know the results in 2011 were not simply “pedestrian”, they were an abomination. Thanks to righties teeing off on him, their .558 slugging percentage and their .329 batting average against him paced baseball.

Part of the reason for this barrage was due to his inability to keep the ball down against righties – which I pointed out back in August. Specifically, Duensing failed to his two main pitches to righties down: his fastball and his changeup. His fastball, on average, finished a little over an inch higher in the zone than it did in 2010. His change, his favored secondary offering to righties, finished nearly two inches higher on average in 2011 over the previous season. Because of this, Duensing experienced a significant spike in the amount of square contact being made. His line drive rate allowed to right-handers rose from 15.7% in 2010 to 22.2% last year.

To be honest, I have had troubles pinpointing what in his delivery has caused this much fluctuation. Video wises, it is hard to pick up on any major changes. Judging from pitch f/x data, however, it would appear that he is dropping his arm angle slightly for his changeup. His average release point on his changeup to righties in 2010 was several inches higher and several inches closer towards first base. This may be an indication that he was been lowering his arm slot when releasing his change thus having it remain up in the zone rather than staying on top of it.

Interestingly enough, the video scouts at Inside Edge did not feel that right-handers actually smashed the ball around off of him as much as his the stats from the previous two paragraphs would indicate. According to them, they concluded that righties had a .236 well-hit average off of him. It was well above the league’s average but 17 other starters saw harder contact including Tampa’s David Price and Arizona’s Ian Kennedy.

So here’s what we know: Duensing’s stuff is stupid good against lefties. If he is limited to a higher portion of left-handed match-ups, as would be the case if he had the luxury of being inserted into those prime situations in a given ball game, he will likely succeed and put up very good numbers. We also know now that he struggles mightily against right-handed opponents. Given a higher pool of those opponents to face in 2011, overexposed Duensing was battered continuously. Then again, he demonstrated in 2010 that when he was able to locate his pitches properly, he was able to keep righties from launching an extra base hit assault (52% groundball rate is not too shabby).  

I tried to make it abundantly clear last year heading into spring camp that his arsenal is best suited for relief. Yes, he had some impressive outings in 2010 but that did not detract from the fact that he would be substantially more effective among the relievers. Without any outside additions or prospects ready to move him from the rotation, the Twins decided to let their good fortune ride. His results in 2011 should more or less solidify this fact in concrete: Duensing is made for the bullpen.