Dylan Bundy Used His Slider to Dominate in August

Dylan Bundy capped a terrific month with a one-hitter Tuesday night, and his strikeout rates are reaching new heights.

Dylan Bundy capped his terrific month of August in style Tuesday night.

The 24-year-old right-hander struck out 12 Mariners and allowed just 1 hit and 2 walks in Baltimore's 4-0 win, delivering his first career shutout and fifth consecutive quality start. The only hit he allowed was a bunt single from Kyle Seager in the fourth inning.

For the month of August as a whole, Bundy posted an ERA of just 2.00 over 36 innings, while allowing a .216 wOBA. These numbers are backed up by solid peripherals, as he has a 28.3% strikeout-to-walk rate, 2.29 FIP and 3.06 xFIP during this period of time.

It is a welcomed development for the young hurler, who had been trending in the wrong direction after a nice start to the season. The below graph shows how his FIP, xFIP, and ERA have fluctuated throughout 2017.

Screen Shot 2017-08-29 at 10.22.26 PM.png

After steadily getting worse throughout the first part of the year, he's turned things around at the perfect time for the Orioles.

More Whiffs and More Strikeouts

From April through July, Bundy’s strikeout rate was just 18.6%, with a swinging-strike rate of 10.3%. The latter figure suggested at least some regression was in store, as the MLB averages in these departments for starters are 20.5% and 9.7%, respectively.

His performance this month has exceeded mere regression to the mean, as he has fanned 32.6% of batters faced, along with opponents swinging and missing at 16.3% of his pitches. This latter figure is tied with Dan Straily for the highest swinging-strike rate this month.

...Along With More Sliders

This uptick in whiffs has coincided with increased usage of his slider, which is his best swing-and-miss pitch. After not throwing the pitch in 2016 -- according to FanGraphs -- it's generated a swinging-strike rate of 24.9%. It's also worth noting that only four other pitchers have a lower contact rate on their slider.

Bundy went to the well for this pitch about 20.0% of the time over the first four months, but that number has jumped up to 27.3% in August. So, why is he throwing it more often? It appears as if this is happening simply because he's found his "feel for the pitch again," according to Jon Meoli of the Baltimore Sun.

"I would say it's gotten back to the consistent movement of it — not so sweepy, and I'm not pulling it as much right now," Bundy said, according to the article. "I'm just trying to concentrate on keeping it down and staying on top but behind it, if that makes sense, and throwing it with some downhill angle to it."

The numbers back this up. In April, opponents had a 27.1% swinging-strike rate against the pitch, per Books Baseball (which also uses Pitch Info data). Over the next three months, that rate dipped down to 19.8% before spiking all the way back up to 34.5% this month.

Not Just the Strikeouts

In addition to his strikeout surge, Bundy has also reduced his walk rate from 7.9% in the first half to 5.3% in the second. His homer rate, though, is probably lower than it should be; he has allowed 1.40 home runs per nine innings, but his home-run-to-fly-ball rate is just 11.8%.

That's two percentage points below league average, and Statcast suggests this is owed more to luck and randomness than actual skill. According to, Bundy “should have” allowed 26.6 home runs so far this season, based on the exit velocity and launch angles of the fly balls he has allowed. In reality, he has only allowed 24.

Then again, like so many other things, he has also improved his performance on contact. His Expected wOBA allowed on contact in August is .329, down from .370 over the first four months of the year, per Baseball Savant (the average xwOBA on contact this season is .360).

While we obviously should not fully buy into a five-start stretch, the apparent change in approach makes it very easy to be optimistic about the promising young righty.