He was mostly missing the corners with his fastball, IIRC. Like wichmae said, he was getting squeezed. He might have missed with a changeup once or twice as well, though I do not specifically remember that. Two points about his slider: First, it's not something he should be throwing for strikes too often. It's a good pitch that's only going to be a swing and miss pitch if he can spot his fastball and change up (much like Wily Peralta can't). The occasional backdoor slider on the corner is fine, but if he's leaving that pitch in the zone it'll be trouble. That's true for almost anyone who throws a slider. Second, as Hammer already mentioned, he should not be throwing that pitch more than necessary. Besides the injury risk, fastball command always has to come first. You can throw slider after slider until the cows come home, but if you're not putting your fastball (or change) where you want it, no one's going to swing at it. Except the bad ones. I'd even argue he should be throwing more change-ups than sliders at this point. His slider is already pretty good. Mastering the change will push him that next step forward.