When the Brewers picked Jeremy Jeffress in the first round of the 2006 draft, they imagined him as their starter of the future. A few up-and-down seasons and failed drug tests later, they lost that vision and moved Jeffress to the bullpen, where he did well enough in the 2010 season to earn a brief promotion to the majors. In the following offseason, they shipped him (along with a few others) to Kansas City in exchange for Zack Greinke. Jeffress never found his footing there, struggling at every level of play before heading north of the border. His story stayed mostly the same for the Toronto Blue Jays, so when he returned home to Milwaukee in July of 2014, no one expected much.
And then, suddenly, everything clicked. Jeffress managed to consistently punch-out batters, limit the amount of free passes, and keep the ball on the ground — all of which helped him to a 1.88 ERA in 28.2 innings for the Brewers last year. Of course, after the hard times that preceded it, a burst like that reeked of luck. And, indeed, a 4.13 DRA overshadowed those runs allowed, and contributed to PECOTA’s relative pessimism (it foresaw a 3.74 ERA).
But Jeffress has, for the most part, kept his success going. His ERA has risen by more than a run, but remains superb at 2.95. Meanwhile, he’s lowered his DRA to 3.72, suggesting that he’s improved his underlying skillset. What steps has he taken to better himself? Well, that’s kind of interesting.
During his lean years, Jeffress leaned on his four-seam fastball, using it for 55.5 percent of his pitches. He combined that with a sinker and curveball, which he threw 21.9 percent and 19.7 percent of the time, respectively. Obviously, that recipe didn’t work out that well for him. While all of those pitches garnered solid amounts of whiffs and grounders, few went for strikes. His sinker carried a respectable 64.9 percent strike rate, but the mediocre 62.7 percent rate on his four-seamer, and the horrid 50.7 percent rate on his curve, negated that.
When Jeffress came to Milwaukee, several things changed. He swapped the four-seamer for the sinker, relying on the latter to the tune of a 69.0 (nice) percent usage rate, as the former shriveled to 7.6 percent. At the same time, both of those saw their whiff rates drop, from 9.2 percent and 11.0 percent to 3.2 percent and 6.0 percent, respectively. The curveball’s ability to fool hitters improved a bit, from 9.3 percent to 10.5 percent, but that couldn’t make up for the losses on Jeffress’s hard stuff.
Instead, Jeffress racked up fouls and looking-strikes. His curveball’s looking-strike rate spiked from 17.6 percent to 32.6 percent, and his four-seamer and sinker each saw a seven percentage-point gain in foul rate. Hitters didn’t put the ball in play as often, which put them in counts that favored Jeffress; from there, he’d ring them up with a called strike. And, obviously, he threw more strikes. Less than a third of his four-seamers and sinkers went for balls, and his curveball’s strike rate rose to 62.8 percent. That step forward elevated his performance to the sub-two ERA that he posted for the Brewers.
Then came this year. Intriguingly, he’s given back some of the gains he made on sinkers: Thus far, he’s thrown “only” 53.4 percent of them, as opposed to 25.3 percent four-seamers. They’ve both gone for strikes a little less often, and have resulted in fouls less often. As with before his breakout, though, they’ve granted him swinging strikes galore, with double-digit whiff rates for both. (Remember that even the best sinkers and fastballs top out at around 6 percent.)
What differed last year to turn those swings and misses into fouls? The four-seamer’s stuff changed somewhat dramatically in 2014 and has since evolved further:
Assumedly, the shift in movement made up for the gain in velocity, to such an extent that Jeffress all but abandoned the four-seamer. It’s since begun to drift back the other way, and the results have returned with it. The story doesn’t change much for the sinker:
He lost some sink on it last year, and it’s since reappeared, albeit at the expense of some velocity. The changes have worked out well overall, as swinging strikes have helped Jeffress stay on top of his game.
But if the four-seamer and sinker have simply returned to his previous career norms, why hasn’t his play declined? The answer: his curveball, which has never performed better. Its whiff rate has surged to 18.9 percent, and its ground-ball rate has come up with that, sitting at 70.0 percent after hanging around the mid-50s before this year. Its plummet in strike rate (to 55.9 percent) and looking-strike rate (to 22.1 percent) notwithstanding, the curveball has dominated.
Unsurprisingly, the stuff on that pitch has had a hand in its hegemony. This season has given Jeffress’s curveball the best of both worlds:
Jeffress has maintained his velocity uptick, and has begun regain the drop that he once had. The aforementioned results, both for the curveball and for Jeffress as a whole, testify to the positive effects of that change.
Coming up through the minors, Jeffress had the kind of stuff that could blow away the competition at every level. It took him some time to fully develop and take advantage of that potential, but now that he has, the Brewers have themselves another exquisite reliever. It’s not where the team saw him nearly a decade ago, and yet they probably can’t complain too much about how it’s turned out.