AaronGleeman.com

Glen Perkins' sore elbow set in a motion of a series of moves that ultimately boiled down to Anthony Swarzak replacing Perkins in the rotation and Sean Henn replacing Craig Breslow in the bullpen. For now it sounds like Perkins has avoided a serious injury, so Swarzak will likely make three starts before heading back to Triple-A, with big-league debut coming Saturday against the Brewers. Swarzak ranked seventh on my list of the Twins' best prospects coming into the season, with this write-up:

Anthony Swarzak got off to a slow start in 2007 before being slapped with a 50-game suspension for violating baseball's substance abuse policy, but had a 2.67 ERA and 69-to-18 strikeout-to-walk ratio in 80.2 innings at Double-A after returning. Despite that strong showing at New Britain the Twins sent him back there last year and he was awful, going 3-8 with a 5.67 ERA and .304 opponent's average in 20 starts before an undeserved promotion. And then of course he went 5-0 with a 1.80 ERA at Triple-A.

Those pretty numbers make it seem like something clicked for Swarzak once he got to Rochester, but in reality his success there came via an awful lot of smoke and mirrors. His strikeout rate actually fell 15 percent compared to what he did at Double-A and his strikeout-to-walk ratio was sub par at 26-to-14 in 45 innings. Swarzak thrived in his first taste of Triple-A because 74 percent of his balls in play were converted into outs, whereas that number was 66 percent at Double-A and 68 percent for his career.

His strikeout percentage has declined with every step up the organizational ladder, going from 26.2 at low Single-A and 21.8 at high Single-A to 18.6 at Double-A and 13.8 at Triple-A. To some extent that's due to moving quickly through the system and reaching Triple-A as a 22-year-old, but that trend casts doubt on Swarzak's ability to be more than a mid-rotation starter. The raw stuff is certainly there to miss more bats and he's still got plenty of time to develop further, but his ceiling has lowered.

Since then he's posted a 2.25 ERA in seven starts at Triple-A, which is no doubt why the Twins chose him over Kevin Mulvey or Brian Duensing to fill in for Perkins and no doubt what most people will focus on when discussing Swarzak's future. However, his 32-to-11 strikeout-to-walk ratio in 44 innings once again failed to match the sparkling ERA and Swarzak now has just 58 strikeouts compared to 25 walks in 89 career innings at Rochester.

Those numbers certainly aren't bad from a 23-year-old at Triple-A, but when combined with the fact that he's a fly-ball pitcher Swarzak's sub par strikeout rate and mediocre control don't predict great success. Now, he throws much harder than the lack of missed bats would suggest and also features a curveball that everyone seems to agree is a strong pitch, so what Swarzak has done at Triple-A thus far definitely doesn't put a cap on his long-term upside.

At the same time, it does signal that the odds are against his thriving in the big leagues right now and indicates that he's currently on track to develop into a mid-rotation starter rather than an ace, which will be something to consider when all anyone wants to talk about is his ERA. Along with adding Swarzak to the rotation the Twins also lost Breslow on waivers, which is disappointing fewer than 48 hours after calling up Henn from Triple-A because both are 28-year-old, left-handed middle relievers.

Breslow has struggled to throw strikes, handing out 11 walks in 14.1 innings, and served up a walk-off homer to Alex Rodriguez over the weekend, but he had a 1.91 ERA and 39-to-19 strikeout-to-walk ratio in 47 innings last season and is simply a better pitcher than Henn. The difference isn't huge and the impact will likely be minimal given the limited bullpen role, but it sure seems like the Twins chose the new lefty reliever over the old lefty reliever just because they felt the need to shake things up.

MAJORS           IP      ERA      FIP      SO%      BB%      GB%
Breslow        89.2     2.91     3.89     19.7     11.9     39.8
Henn           50.0     7.20     6.60     15.2     15.2     38.0
 
TRIPLE-A         IP      ERA      FIP      SO%      BB%
Breslow       144.2     3.42     2.94     25.8      8.1
Henn          113.0     3.58     3.24     21.5     10.2

The above stats ignore how Henn fared as a full-time starter, so it's an apples-to-apples comparison of relief work. Breslow has been significantly better as a major-league reliever, with 30 percent more strikeouts, 22 percent fewer walks, and a huge edge in ERA and FIP. The gap isn't nearly as big when it comes to Triple-A numbers, but Breslow still holds a clear advantage in strikeouts, walks, and overall performance. He's just a better pitcher, period, and not surprisingly the A's plucked him off waivers.