David Robertson has returned to dominance

After more middling seasons than I can count (or that I’d care to count; the point is, I’m lazy), the White Sox finally decided to rebuild this winter. Chris Sale and Adam Eaton left, and a boatload of prospects came in. My colleague Henry Druschel speculated in December that the team would trade Jose Quintana, Jose Abreu, and Todd Frazier, and while each of those stalwarts remains in Chicago for now, they might be on the move in a few months.

One big-name player Henry omitted from his listicle analysis: David Robertson. The White Sox reeled Robertson in during their 2014-15 offseason spending spree, signing the ex-Yankee to a four-year, $46 million deal. In his first two campaigns on the South Side, Robertson wasn’t as sharp as he’d been in the Bronx; over 125 ²⁄₃ innings, he put up a 3.44 ERA and 3.04 FIP. Those numbers, while respectable, didn’t make him an appealing trade asset.

But he’s turned things around to start 2017. Robertson has faced 13 batters this year; eight have gone down on strikes, and zero have earned a free pass or hit a home run. The result? A 0.00 ERA and -1.07 FIP (not a typo) in four stunning innings. If Robertson can come anywhere close to sustaining this over the remainder of the season, he’ll fetch a handsome return at the trade deadline.

Robertson, like many relievers, relies on two pitches — a cut fastball and a curveball. He’s typically used the former as his bread-and-butter pitch, busting out the latter as his haymaker. This year, though, he’s flipped the script, and dealt haymakers nonstop:

Image via Brooks Baseball

Robertson’s curveball has long been one of the best in baseball. It combines above-average velocity (82.0 mph) with above-average drop (7.5 inches); as Eno Sarris explained at Fox Sports back in 2015, those are the most important things for a curveball:

* If you want whiffs from your curve, throw it hard.

* If you want grounders from your curve, make it drop.

Indeed, Robertson’s curve has always been better than his cutter, in pretty much every regard:

Plus, the curve has consistently improved. As Robertson has thrown it lower in the zone every year, its swinging-strike rate has continued to climb, spiking in 2017:

Image via Brooks Baseball

I wouldn’t expect Robertson’s curveball to have a 36.7 percent whiff rate for the entire season — just as I wouldn’t expect him to maintain a 0.00 ERA. With this new, curveball-heavy approach, though, he should continue rolling.

Why did Robertson adjust now? For most of his career, he’s lived on called strikes, not swinging ones. That’s an area where his cutter (25.9 percent called strikes) rises far above his curve (14.9 percent called strikes). But during his first two seasons with the White Sox, Robertson couldn’t catch hitters looking like he used to:

Image via FanGraphs

Of course, things have changed quite dramatically this year, as opponents haven’t adjusted to this new version of Robertson. They will, in time, and his ERA will rise. But going the Rich Hill route — i.e. throwing a ton of curveballs — makes him a new, and dangerous, relief pitcher.

For the White Sox, it’s a totally new year. While the team isn’t very good, the future looks bright — and with Robertson pitching this well, it could get a whole lot brighter. Out with the old…

GIF via MLB.com

…and in with the new:

GIF via MLB.com

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.