Kyle Gibson has hit a slight rough patch

On Tuesday night, Orioles starter Tyler Wells explained to reporters that sometimes as a starting pitcher, you show up to a game with your A stuff, sometimes your B stuff .... and then there is whatever Kyle Gibson was heaving up in Kansas City last night. (Okay, Wells didn’t say that last part.)

On Wednesday night, Gibson threw five one-run innings, but his outing unraveled with a four-run seventh inning. More importantly, he didn’t strike out a single hitter all game. In fact, Gibson drew just one whiff in forty swings, the worst rate of his entire career (2.5%).

Why does this matter? According to the folks at Pitcherlist, one of the most important metrics in defining starting pitcher success is CSW% (called strikes + whiffs/total pitches). Both called strikes and swing-and-misses tend to correlate strongly with pitcher-controlled outcomes, to stay consistent over a pitcher’s career (ten starts is what Pitcherlist suggests as a good sample size), and, most importantly, they’re a good general test of how dominant a pitcher’s “stuff” is.

Here’s roughly how CSW is cashed out:

On Wednesday, Kyle Gibson’s CSW was 14%. That’s bad enough that the “Poor” category doesn’t even start for six percentage points after that.

From this POV, Gibson’s five one-run innings seem like a blip of massive good luck. That same day, batters hit .370 against him, boasted a crazy 60.7% hard-hit rate, and posted an average exit velocity of 91 mph, Gibson’s highest of the season. He wasn’t fooling hitters at all, and this is the Royals, not the Rays.

So that’s the bad news. The good news: it’s been two outings in a row now that Gibson has looked a little off. Good news, you say? Well, yes. In relative terms.

On April 27 against Detroit, Gibson allowed eight hits in 4.1 innings, giving him a 6.23 ERA for the game. But his peripherals never got as bad as they did this week. For comparison, that day Gibson allowed a 90.5 mph average EV, a 33% hard-hit rate, and a 25% CSW, which, says Pitcherlist, is “Okay.”

The start before that, on April 22, went pretty fantastically for him: Gibson struck out 11 hitters with just two hits and one run allowed. Again, to compare peripherals, on 4/22 Gibson’s average EV was 85.7 mph, his hard-hit rate 50%, and his CSW an off-the-charts 44.8%. (That’s off the charts in the other direction now—it was better than excellent.) Batters averaged a paltry .095 against him. So Gibson is capable of getting swings-and-misses. He just didn’t this week.

Three recent Gibson starts, three very different outcomes. Is there a clear difference between Good and Bad Gibson?

It’s not about throwing strikes: Gibson is a strikethrower, and even in Wednesday’s meltdown he was in the zone about 66% of the time.

It is about pitch selection. Gibson has six pitches in his arsenal, which is cool, but some are better than others. In his excellent start (4/22), Gibson leaned sinker (33%), sweeper (24%), and changeup (21%). He threw a single fastball all game. In his OK start (4/27), he threw mostly changeups (25%), plenty of sinkers (21%), and then a near-even three-way split of sweepers, cutters and fastballs (about 15% each). On Wednesday, when he was bad (5/3), he threw more fastballs than any other pitch (30%), then sweepers (19%), sinkers (18%), and cutters (16%).

We appear to have a rough correlation, something to the effect of “The more heaters Kyle Gibson throws, the worse his start turns out.” In practice, Gibson’s pitch mix seems to be a matter of strategy, because it varies quite a lot: generally the worse-hitting the team, the more plentiful the heaters, which probably makes sense. Consider Gibson’s fastball percentage alongside his ERA for each start: vs. Boston (13.9% FB, 7.20 ERA), Texas (21.6%, 2.57), Oakland (20.7%, 1.42), Chicago (3.1%, 6.75) and Detroit x 1 (1%, 1.42) but Detroit x 2 (13.7%, 6.23), and this week, against Kansas City (30%, 8.11).

This is all kind of crude (obviously opposing hitters’ talent matters, duh) but it does suggest that Gibson’s worst days are his most fastball-reliant ones. Lo and behold, batters are hitting .375 and slugging .938 against that pitch, not to mention .429/.571 vs. his two-seam cut fastball. I’m no pitching coach, of course, but I think I’d tell Kyle Gibson to throw fewer fastballs.

So pitch selection matters. But—back to the “A stuff, B stuff” thing—so does quality. On Wednesday, the Gibson sweeper averaged 2 inches less break than usual, the changeup 3 inches less, and the sinker 1 inch. (His fastball was normal.)

So, in short, a poor Kyle Gibson outing against a weak-hitting Kansas City lineup may be explained by, one, breaking/offspeed pitches that didn’t have a lot of break, and two, more heaters than usual (perhaps to compensate for the wonky offspeed stuff, or perhaps just because this was the gameplan all along), also getting hit hard. A not-so-winning recipe.

Sometimes appearances can deceive, just like Gibson’s five one-run innings had me thinking this was shaping up to be a great start, despite the absence of whiffs. In the end, Kyle Gibson brought his “C stuff” to Kansas City (officially his worst outing of the season per the data) and CSW came back to bite us all.

There’s good and bad in that: “average,” for Gibson, looks better than six runs in 6 2/3 innings. Does it look like greatness? Not likely, although maybe if his new sweeper keeps sweeping. Otherwise, as CC’s Alex Church pointed out yesterday, the O’s should continue to expect great things from their bullpen, but somewhat less from the starting rotation. So far this team has largely compensated for its faults. Could a pitcher trade be in the cards come mid-season? You kind of have to hope so.