If you were to merely pull up the stats for Corey Oswalt thus far in the big leagues, you probably wouldn’t be impressed. He’s thrown 33.1 innings over six starts and one relief appearance, and he has a 5.13 ERA and 5.41 FIP. His strikeout rate is pedestrian—at 6.21 per nine or 17.2 percent—and he’s given up 1.89 home runs per nine innings.
But over his past five appearances, all of which have been starts, Oswalt has looked quite a bit better. He’s only totaled 26.0 innings, but he has a 3.81 ERA over that stretch. For context, the major league average for starters this year is a 4.20 ERA. His strikeout and walk rates are pretty consistent with the full-season numbers, but he’s given up a much more reasonable 1.38 home runs per nine. We’re dealing with arbitrary end points and small sample size data all around here, but the recent success has at least sparked the idea that maybe Oswalt could be a viable major league starter going forward.
As for his repertoire, Oswalt has thrown a four-seam fastball, sinker, curveball, and changeup thus far in his big league career, according to Brooks Baseball. In terms of velocity, he’s on the low end. The four-seam has averaged 91.1 miles per hour, while the sinker has averaged 90.3. But that hasn’t stopped him from relying on the fastball, as the pitch has been trending upward in usage over his appearances since the beginning of July.
Generally speaking, he’s thrown his changeup more often, too, even though it’s still been thrown the least often in most of his appearances. In his start against the Braves on August 5, the change was second among his pitches used for the first time in a major league appearance. And over his last three starts, he’s gotten eight swings-and-misses with the change in the 42 times he’s thrown it—good for a strong 19.0% swinging strike rate.
Whether or not the usage and swinging strike rates continue to trend in that direction for the change, the pitch hasn’t turned Oswalt into a strikeout machine. In fact, he’s struck out even fewer batters per nine over those three starts than he has on the season as a whole. But he does have a 3.38 ERA over those starts.
Whatever Oswalt may or may not be at the major league level, it’s blatantly obvious that the Mets should continue using him as a starting pitcher the rest of the way to see if they might actually have a viable back-of-the-rotation starter in him. Mickey Callaway hadn’t sounded like keeping Oswalt in the rotation was a priority as recently as a few days ago, but there was a mention that the team might go to a six-man rotation if and when Steven Matz comes off the disabled list. Even if Matz returns soon and the Mets prefer a five-man rotation, there is no way that Jason Vargas should get starts at the expense of Oswalt.
In the end, maybe things don’t work out and this stretch of success looks like a blip. But the only way of finding out whether or not Oswalt might be able to sustain it is by playing him.