|San Deduno on Monday walked five and struck out six.|
He also won. Again.
That's the good stuff. On the other hand, he's averaging less than six innings a start (40 innings) and he's walked more men (30) than he's struck out (28). You have to go a long ways back into baseball history to find effective pitchers with that kind of BB/K ratio.
He's gotten away with it because he's not giving up a lot of hits. On Monday, he yielded five hits in seven innings; he has yet to allow more than six in any of his starts.
His BABIP — Batting Average on Balls In Play — is .252, which is absurdly low. It has become a basic tenant of sabermetrics that pitchers have relatively little control over BABIP, that over time, pretty much every pitcher's BABIP will be around .300. (Randy Johnson, to pick on a hard-to-hit pitcher, had a career batting average allowed of .221, but a BABIP of .295.)
What pitchers can control: Walks, Strikeouts, Home Runs. Deduno is weak on the first, mediocre on the second, acceptable on the third. All of which suggests that his success will be short-lived.
If we're looking for reasons to believe, however, I'll offer this thought: Knuckleball pitchers tend to be an exception to the BABIP principle. (Tim Wakefield's career BABIP was .276, Charlie Hough's .253. These are guys with long enough careers that those numbers are no flukes.)
Deduno doesn't throw a knuckleball, but by all accounts his fastball acts like one — it moves in different directions and he doesn't know which way it's going when he throws it. As with a knuckleballer, his catchers are setting up in the middle of the plate and trying to react to the movement.
The Twins are desperate enough for starters that they will certainly keep giving Deduno chances to fail. Even if his success is sustainable — and that's hardly proven — he'll need to work deeper into games to be more than a rotation filler.