How is Anthony Swarzak so dominant?

As May progresses and we approach the one-third mark on the 2017 MLB season, we can start to discern the small-sample flukes from the legitimate breakouts. Jason Vargas looks like he might be the real deal, while Avisail Garcia is coming down to earth, as expected. This is the period when the true stars begin to separate from the pack.

David Robertson has returned to dominance

Jesse Johnson-USA TODAY Sports

The White Sox might have another trade chip.

One player’s unbelievable start has — at least among the sabermetric community — gone under the radar, for the most part. Coming into 2017 with a lifetime ERA of 4.52, Anthony Swarzak has allowed three earned runs in 19 ²⁄₃ innings for a 1.37 ERA. His 1.91 DRA is one of the best in baseball, as is his 80 cFIP. He’s striking guys out like crazy, throwing a ton of strikes and avoiding hard contact; in pretty much every way, he’s dominating.

Swarzak’s success is a bit strange, at first. He appears to have a number of things working against him:

• A pedestrian fastball — One hundred twenty-three relievers have thrown at least 100 four-seam fastballs this year. Swarzak’s heater ranks 64th in average velocity (95.0 mph), 76th in average horizontal movement (-5.5 inches), and 23rd in average vertical movement (10.6 inches). While it rises a little more than average, the mediocre velocity on Swarzak’s fastball would seem to undermine it. (It doesn’t have a great deal of spin, either, in case you were wondering.)
• Subpar command — To this point, Swarzak has a -0.50 percent CSAA, Baseball Prospectus’s measure of how well a pitcher hits his spots; that ranks 192nd among 303 hurlers with 15 innings. According to Bill Petti’s data, Swarzak has thrown 26.6 percent of his pitches on the “edge” of the strike zone, placing 143rd among the 360 pitchers with 200 pitches. Swarzak can’t dot his heater on the corners as some pitchers do.
• A standard delivery — No Carter Capps nonsense going on here:

GIF via MLB.com

But Swarzak’s sublime start is no anomaly. The secret to his excellence lies in a few places.

Swarzak’s fastball might not stand out velocity-wise, but his slider certainly does. He’s thrown the pitch at 87.1 mph this year, the 23rd-highest mark in the majors. Together with its surprising rise — it ranks 25th with 2.5 inches of vertical movement — that’s given it a 25.7 percent whiff rate, which places sixth.

The slider has a pretty standard path — it’ll usually dart low-and-away to right-handers:

Image via Brooks Baseball

Just five other pitchers — Jesse Chavez, Zack Greinke, J.J. Hoover, Ricky Nolasco, and Michael Fulmer — have thrown more down-and-away sliders than Swarzak. And he’s thrown the pitch an astounding 55.2 percent of the time this year, which only Chris Young and Andrew Miller can top.

The slider, of course, isn’t alone. Its movement contrasts splendidly with the fastball, which Swarzak has pounded the zone with:

Image via Brooks Baseball

Swarzak’s four-seamer ranks in the top 20 percent of MLB in zone rate. By tempting hitters with sliders in the dirt, he’s been able to sneak his fastball by them for whiffs (18.1 percent, ninth in MLB) and strikes (74.3 percent, fifth in MLB). This is where the aforementioned rise on the four-seamer comes into play — he can get hitters to undercut at a fastball if they’re trying to defend against a low breaking ball. He has only these two pitches, but that’s all a reliever needs.

White Sox pitching coach Don Cooper has tried to get his hands on Swarzak for a couple of years, and we can see why. The righty labored in anonymity for years, but with his dependable fastball playing off his high-octane slider, he’s broken out for the South Siders. While it might take a bit of digging to see, there’s nothing fluky about Swarzak’s dominance.

Ryan Romano is the co-managing editor for Beyond the Box Score. He also writes about the Orioles for Camden Depot, sometimes. Follow him on Twitter if you enjoy angry tweets about Maryland sports.