It's not hard to see why Matt Harrison was a well regarded prospect back in the day. Tall lefty with a big fastball and multiple off-speed offerings? Everybody wants those. But so far he really hasn't put it all together and the result is a not exactly eye-poping 5.24 career ERA. Even so, he's pretty likely to get plenty of chances given his 92-94 mph southpaw heater. He could probably be an asset in the bullpen right now if the Rangers had better starters, but they don't so for now he's a 4/5 masquerading as a number 3.
Which is not to say his heater is perfect. First, the pitch doesn't help him with its movement. It's not a true four-seam riser, nor does it bore and sink like a good two-seamer. It's stuck in the middle so anytime he doesn't have the platoon advantage, it goes from a true plus pitch to maybe a tick above average. It's not enough to make a big leaguer flinch, except when he really rears back. Every now and then he'll pump it up to 95 or 96, though he doesn't seem to save it for the strikeout.
The bigger issue, the reason the pitch overall rates as no better than average, is a lack of command. He misses often enough by half a plate and it doesn't seem like he knows which side it'll miss to. So he's not a nibbler, he just goes through long jags where he can't put the ball where it needs to be. This hurt him badly in his start on the 6th against the Yankees, particularly in the first inning.
He started Jeter off inside, about thigh high for a strike, hitting the glove dead on at 95 according to the FSN radar. The next pitch was a curve he left up and got away with thanks to an ugly swing. That put him up 0-2 and Napoli set up way low and in, trying to get Jeter to chase. Instead Harrison repeated the first pitch of the AB and gave up a single to that patented inside-out swing. Nothing terribly damaging, but the inability to finish off a hitter after getting way ahead is a classic symptom of the commandless pitcher.
Granderson followed and Harrison wouldn't be so lucky. A bad miss low and in with the fastball was followed by a bit of a gift from the umpire on a fastball up and a little too out. 1-1 and Granderson has yet to see anything offspeed. Napoli moved back inside to try to get another heater under the hands. But once again Harrison lost it, this time over the heart of the plate. Upper deck shot, 2-0 Yankees.
That's 6 pitches, 5 fastballs, no whiffs. Yes, it's a positive that Harrison likes to move the fastball up and down, in and out, but the problem is that he doesn't have a spot that he can consistently hit. He did his best work to his glove side all game, but that isn't saying all that much.
Which brings me to his offspeed issues. That 0-2 pitch against Jeter was a chance for a strikeout and Harrison has other pitches in his arsenal. Between his cutter, curve and change, you'd think there was a pitch he'd feel comfortable going to. But his command issues leaked over here as well. The cutter was axed for the evening, presumably because he just wasn't feeling it in warm ups. The change was not totally absent but it might as well have been. He threw 11 of them, none for swinging strikes.
As has been the case throughout his career, he wasn't much more than a 1-pitch pitcher against right handed batters. This isn't always true, as he hasn't given up on his offerings and shows flashes of both plus change and cutter. In his start against the Angels on April 20, he had both arrows in his quiver that night. Not coincidentally, his fastball command was also there where it hadn't been before and suddenly he looked like the pitcher that John Sickels gave a B+ grade to in 2008. While he still missed often enough with all of his pitches (change left up for a HR to Kendrick, fastball up to Bourjos went for a triple), the mix of pitches kept hitters off balance. His fastball/curve combo is enough for lefties and a fastball/cutter/change combo is, as we've seen with John Danks, plenty thwart righties.
So part of the plan of attack is limiting the number of lefties in the lineup given his fastball. But the rest is dependent on which Harrison shows up. If he's struggling with his command and not showing the offspeed, then it's a simple matter of not helping him out. He'll move the ball around, but eventually he'll make a mistake that his velocity can't overcome. If he's showing the cutter but not the change, ignore anything low and in. Even when it's on, he still hasn't really shown he can spot a cut fastball on the hands like we've seen Danks do time and again.
If it's the change that's there, then you sit middle in. If he's got all three working, righties are in a tough spot but patience still remains key: even when he's feeling his pitches, he's still not experienced enough to command them consistently. Walks will always be on the table, there will just be fewer opportunities for extra bases. Like most starters in the bigs, everybody has their day at least now and then. Harrison's track record suggests that he's not often on, so you have to make him prove he his best stuff and location.