Through two months, Phil Humber has the best ERA of any starter on the White Sox, largely thanks to his offspeed offerings.
Two months ago to the date, Humber made his White Sox debut—and it wasn't good. He threw two pitches, allowing a bunt single to Orlando Cabrera on the first and a ground ball base hit to right to Travis Buck. The two singles loaded the bases, and with the left-handed Jack Hannahan next up, Humber was pulled in favor of Matt Thornton. A single and a sacrifice fly later, both of Humber's runners scored, leaving him with the line of zero innings pitched with two hits and two runs allowed. On two pitches.
Humber again came out of the bullpen April 6, tossing a pair of scoreless innings in the White Sox's extra-inning win over Kansas City. I was in attendance, and I distinctly remember saying "oh no, here comes Humber" when he jogged in from the bullpen. He was fine in that game (which, by the way, had an awesome win probability chart), and then entered the starting rotation with a fantastic outing against Tampa Bay, throwing six innings of one-run ball with four strikeouts and two walks.
But Humber struggled in his next two starts, allowing four runs in 5.0 and 5.1 innings, respectively. It wasn't until April 25 at Yankee Stadium that the Legend of Humber was born.
Against one of baseball's top offenses, Humber took a no-hitter into the seventh. He allowed no runs on one hit with five strikeouts and no two walks, giving the scuffling Sox a much-needed boost. From April 25 on, Humber has thrown fewer than seven innings just once and allowed more than three runs just once.
The keys for Humber—beyond luck, if that's your thing—have been his two main offspeed pitches. His fastball and slider have been above average, but nowhere near as good as his better offspeed offerings.
Humber's two best pitches this season have been his 12-6 curveball and his straight changeup. Since entering the rotation, he's thrown his curveball on 24.6 percent of pitches; his changeup, 22.1 percent. Humber's effectiveness with his curveball has been key in his turnaround, as it's gone from a good to a great pitch.
Of the 233 curveballs thrown by Humber (according to Texas Leaguers' pitch f/x database), 63.1 percent have been strikes. Twelve percent of those curveballs have resulted in a swing and a miss, nearly double the whiff rate of Gavin Floyd's curveball.
Humber's changeup has similarly baffled opponents. Of the 210 he's thrown, 64.3 percent have been strikes, with hitters whiffing on 13.8 percent of the pitches.
But Humber rarely uses his changeup as a put-away pitch, usually opting for it to keep hitters off-balance in 1-0, 1-1 and 2-1 counts. As soon as there's a chance for a strikeout, Humber goes to the curveball, throwing it over 50 percent of the time on 0-2, 1-2 and 2-2 counts.
Humber isn't a strikeout pitcher, though. In case his 5.05 K/9 doesn't convince you, Humber's only thrown three curveballs in 38 instances of a 3-2 count. Instead, he's thrown his fastball on half the pitches and his changeup on 34.2 percent of offerings. It's no surprise, given these numbers, that Humber has a walk rate of 1.86 free passes per nine innings.
It'd be easy to say hitters could adjust by simply laying off Humber's curveball in two-strike counts, but when three in five go for strikes that probably won't work. To avoid those two-strike curveballs, opponents need to attack Humber early in the count—which is where his changeup comes into play. He'll also occasionally mix in a slider that's done a nice job keeping hitters off balance, as opponents have whiffted at 12.5 percent of the 72 sliders Humber's thrown.
One of my bigger concerns regarding Humber has been that his success has partly been a product of the league not catching up to him. Nobody has ever seen Humber pitch like this, so even if a hitter faced Humber in the past, it's as if he's a completely different pitcher. As scouting reports become more refined and opponents have seen the new-and-improved Humber a few times, they'll be able to make adjustments. And unless he makes adjustments based off his opponents' adjustments, he'll struggle.
The good news for Humber is that his current, fairly-predictable pitch selection gives him a lot of wiggle room to adjust later in the season. If opponents start jumping over his fastball or changeup early in counts, Humber could resort to throwing his curveball on 0-1, 1-1, 2-1, etc. That could take away his curveball later in counts, but it could open up the changeup on two-strike counts. Or he could start mixing the slider in more early in the count to protect his curveball for later.
Humber can similarly adjust to a luck regression—his BABIP won't stay in the low .200s forever—by opting to shoot for more strikeouts. His curveball is already established as a fine strikeout pitch, but maybe incorporating more fastballs—preferably ones just outside of the strike zone—with two strikes could open the door for changeups and sliders to wriggle into his two-strike selection. Both those pitches generate swings and misses at a slightly better rate than his curveball outside of 0-2 counts, so it's worth a shot.
That being said, Humber shouldn't opt for a pre-emptive strike against a future regression that could potentially mess up this equilibrium he has going right now. He'd be smart to ride out whatever combination of good pitching and good luck he has going on right now until it runs out. When that happens, then he can make adjustments.
But that regression hasn't happened yet. And when it does, something tells me Humber will continue to pitch well enough to justify staying in the starting rotation all season.