Let's see if I finish before the game starts!
Guthrie lives and dies on his big fastball. It averages 94 mph and he gets more than his fair share of whiffs with it. In addition, righties have an impossible time getting any lift on it, and while lefties have a better time of it, it's still not a weakness. So in and of itself, the heater can get outs without much additional support, especially when he spots it, which isn't usually a problem. In fact, Guthrie has above average command of all his pitches.
This would be bigger cause for concern if he had better secondary stuff. He's almost entirely fastball/slider to RHB and the slider just doesn't seem to be that great. In '08, he gave up a .351 ISO throwing it about a quarter of the time to right handed batsmen. This should be a boon to hitters like Q! and JD who suffer at times with the slider away. With less trouble determining between the fastball and slider, they should be able to hit each harder. Josh and BA may struggle, though at least Josh excels at hitting offspeed pitches.
To lefties, he dials back the fastball usage a bit and includes a curve and a change on top of the aforementioned fastball/slider combo. He mixes his offspeed more or less equally and gets decent results from them, but there's no devastating offering. The change is the strikeout pitch and it is a good pitch, but it's nothing these batters haven't seen before. Thome, AJ and Getz are all well primed for his junk. It's how well they do with the fastball that will be the determining factor.