While we have little concrete predictive ability in anticipating injuries based on a pitcher's mechanics, using a pitcher's workload as a predictive engine shows much better, though still loose at best, results. Namely, large increases in pitches in one year seem to increase the chance for injury in the next. That makes intutive sense from just a workout perspective. If you had typically been running three miles a day and then decided one morning to go out and run a full marathon, you might get through it, but the next day when you went to go running, you might find yourself more likely to be sore.
In other words, it's always a good idea to build up your strength levels gradually rather than attempting to do it in large chunks. With pitchers, we generally measure that in innings pitched (though some metric based on number of pitches, pitches per inning and pitches weighted by LI would be better equipped to measure stress). The general rule is that you want pitchers to take no more than 40 IP leaps from year to year.
In 2007, pitching exclusively out of the bullpen, Brandon Morrow threw 63.1 innings. Last year, in a mix of relief and starting, Morrow recorded 95.1 innings. Immediately you should see why expecting Morrow to log anything close to 200 innings this year wouldn't be a great hope to rest on. This is further exacerbated by Morrow's use in college, where he didn't spend a lot of time starting until 2006, a year in which he collectively pitches 112.2 innings.
Ignoring 2006, we would think that 130 innings or so would be the max for Morrow in 2009. That appears to be a fair estimate. Factoring 2006 in, there might be some clues that his body would adjust to 150 or so innings without too much trouble, but that is probably the limit. Couple Morrow's young age - he turns 25 in late July - with the injury he already showed this Spring, (which, by the way, he now says is behind him, giving him a shot at breaking camp in the rotation) and it seems wise to be rather cautious with Morrow's workload this season.