How Was Dylan Bundy's Second Half Different?

In his first full season as a major league starting pitcher only, Dylan Bundy started 28 games and threw nearly 170 innings. But his innings were curtailed in the second half, and he was given extra rest between some starts. The additional days off appear to have been beneficial:

1st half: 108 IP, 4.33 ERA, .326 wOBA, 7.0 K/9, 2.92 BB/9, 4.88 FIP, .271 BABIP,
2nd half: 61.2 IP, 4.09 ERA, .277 wOBA, 9.92 K/9, 2.34 BB/9, 3.51 FIP, .277 BABIP

In the second half, Bundy increased his strikeouts and cut down his walks. Oddly enough, batters hit the ball harder against him, though it didn't seem to matter much:

1st half batted ball: 19.6 Soft%, 45.5 Med%, 34.9 Hard%
2nd half batted ball:13.8 Soft%, 46.7 Med%, 39.5 Hard%

Bundy induced more ground balls in the second half, and there weren't as many line drives hit against him. There weren't as many home runs, either (1.50 HR/9 vs. 1.17).

Maybe it's not surprising to find out that Bundy threw a tiny bit harder in the second half. Bundy's velocity on his four-seamer went from 92.3 mph to 92.7 mph. He also threw the rest of his pitches --his changeup, slider, curveball -- slightly harder as well.

But what's more interesting is Bundy leaned more heavily on his slider in the second half. Here's a breakdown of his pitch usage in both halves:

1st half: 53% four-seamers, 11% curveballs, 20% sliders, 16% changeups
2nd half: 55% four-seamers, 9% curveballs, 27% sliders, 9% changeups

Last season, Bundy's slider was his most effective pitch. Here are the numbers against his four offerings, from Brooks Baseball:

Four-seamer: .288/.498 (batting average/slugging percentage)
Curveball: .167/.381
Slider: .174/.252
Changeup: .229/.419

Bundy's slider is a very good pitch, but he has considered not throwing it quite so much. Check out this January article from the Baltimore Sun's Jon Meoli on Kevin Gausman and Bundy, which includes this nugget (emphasis added):

... Bundy has spent the offseason preparing for a heavier workload and examining where he could improve. He started throwing about a week later than normal in an effort to save his arm, and pondered mixing in his curveball and changeup more often as he became too reliant on his slider as an out pitch in 2017.

Did Bundy become too reliant on his slider? Was he not throwing it enough? Or maybe throwing too many of them is not the best thing for a pitcher's arm. That last part is up for debate and is only a guess, and Bundy knows his arm better than anyone else.

The Orioles need Bundy to be just as good or better in 2018 while increasing his workload. He'll seemingly have no limitations, and if healthy, should approach 200 innings.

He's still learning what works best for him now that he's back to being a full-time starter. Bundy is closer to a middle-of-the-rotation option than a frontline starter, but the O's are in no position to complain. It would just be nice if Bundy had more help.

Stats via FanGraphs and Brooks Baseball. Photo via Keith Allison.