The most notable thing about Armando Galarraga's performance last year was his luck. He gave up just 152 hits in 178 2/3 IP for a very helpful .247 BABIP. Subsequently, he had a 3.73 ERA but a 4.88 FIP: he's about a run per nine innings worse than his performance last year suggests. Baseball is a funny thing, Stone Pony. You can get 180 above average innings out of a total nobody.
There may, however, be less regression in the works because Detroit has substantially upgraded its infield defense. There's a good argument that they have the best defensive infield in the game. Between that and Granderson covering center, the defensible balls Galarraga allows will continue to turn into outs at a better than average rate. Anything that leaves the park is excepted in BABIP, of course, and that happened to be a problem for Armando in '08 to the tune of 1.4 homers per nine.
HR rate will fluctuate from year to year, but there are inherent problems with his stuff, particularly against lefties. PECOTA expects that his LH/RH splits will be larger than average:
LHB - .271/.369/.454
RHB - .256/.326/.405
He's entirely fastball/slider to right handed batters and both pitches are fairly average, but the latter plays up thanks to outstanding command. He can get ground outs and whiffs off the slider and he throws it as much as he throws the fastball, a mix that suggests that major leaguers have a hard time discerning between the two. JD and Q! have demonstrated their vulnerability to such pitching in the past by striking out, while Paulie prefers to roll over and hit ground balls to the left side. Recognition will be the key and I expect struggles early if Galarraga is throwing enough sliders.
To lefties, he adds a change-up that he uses to get ground outs, but he misses often and doesn't get whiffs with it. It goes well with his away-away-away philosophy and has its uses, but it isn't an incredible pitch. It plays up depending on the batter's understanding of how Galarraga is trying to get outs. His slider still gets a solid amount of whiffs and groundballs, while his fastball was killed in '08. The program would be: sliders in, changes away and fastballs to both sides to set up each. The problem is the fastball, with which he'd prefer to nibble thanks to its relatively useless rise/run and middling velocity.
As he showed against the Rangers, he can have success if he's hitting his spots, but the stuff is really not that impressive. If you can get him to work his fastball on the plate, he'll start missing in and batters can capitalize. If he's mixing fastball-slider to batters that can't tell the difference, he'll dominate. This will be a nice time to get Brent Lillibridge out of the lineup and get Chris Getz back at the top. It wouldn't be the worst idea to get Wilson Betemit in the lineup, either, though at the expense of whom? Paulie, perhaps, but there's no obvious gain to be made at this point in the season. Number 300 went a long way and Zach Miner isn't really all that different from Galarraga.