The impression I've had of Santos, limited as it must be, has been positive. Especially since he's a cheap Rule V guy, I'd be stunned if the Pirates don't keep him in the rotation, should he continue to pitch as he has so far. As Dejan Kovacevic describes today, his now-ugly spring numbers, ERA etc., will come down if he keeps up the good-enough work.
If you are not familiar with Santos, and why should you be, here's a description of his pitching style from the above link:
He is not a power arm, leaning hard on a first-pitch curveball, as well as a variety of fastballs, a slider and a changeup. When he is on his game, he keeps hitters guessing.
Santos looks well ahead of Vogelsong, I'd guess, who was awful just an inning ago in the Red Sox game. I have WEEI on. The two crusty guys in the booth, who I guess to be Joe Castiglione and some color guy (not Jerry Trupiano, who just came on) had some terse words. "This guy doesn't have very good command," the one said. A few minutes later, the other adds, "His command is seriously lacking." John Hershbeck is behind the plate; he is, if I remember right, one of the more generous homeplate umps.
Vogelsong came back, just after I wrote the above, and he worked a clean 1-2-3 inning.