It’s hard to get too worked up over superlatives in early May. Right now your National League ERA leader is Chris Paddack, Cody Bellinger is hitting like Barry Bonds, and the Rays and Twins are the top teams in the American League. Maybe these things are true. Maybe it’s all a ruse, clouded in sample sizes. We don’t know yet. Things change in baseball, new faces become stars and new teams become powerhouses, but it’s a bit early to get too worked up.
So you’d be right to think that what Atlanta Braves reliever Luke Jackson is doing right now is a little untenable. Here we have a 27-year-old bullpen arm of no real remarkable history, somehow battling for the lead in ground ball rate with the likes of Zach Britton, and making a leap from “guy you see in the sixth inning” to “guy you don’t want to see if you’re the other team”. On a legitimate contender like the Braves, Jackson is beginning to find himself their best bullpen option, and he’s done it by changing what he does as a pitcher.
There was no real reason to be excited for Jackson’s third season in a Braves uniform. Though he struck out a quarter of batters faced in 2018— up more than 10 percent from a year prior— he walked 11.4 percent and forced a grounder just 47.8 percent of the time. It’s your typical middle reliever type of numbers. The K-rate jumped to 29.2 percent so far this year, the walk rate fell a bit to 9.2 so far, but that incredible ability to kill worms this season is a sight to behold. Not to simplify, but there’s a basis of understanding what he’s doing differently by looking at two simple charts:
As a reliever, he leans heavily on that fastball/slider combo, though I did eliminate his curve from those charts. That pitch is seen about 13 percent of the time this year, so it’s more of a fiddle-about pitch than a true tool for him. But what we see here is a swap the last couple years of his fastball usage versus slider usage, combined with an increase in velocity in 2019. We’ve seen that non-fastball usage rise the last several years for relief pitchers, with this season bullpens throwing fastballs just 54.6 percent of the time, an all-time low rate. So Jackson is just following trends. Though really, he’s one of the vanguard of this incredible switch.
More than that though, is the willingness to throw the slider in a lot of other situations. Basically, outside of a 3-0 count, you’re as likely to see a slider (or maybe just not a fastball) from Jackson as you would that four-seam:
Adding to this indecision he’s implanting in the batter’s head, Jackson is throwing that slider in the zone 38.8 percent of the time this year, a seven point leap from last season. So whatever the plan may be to face Jackson, and especially if it’s based on a book from a year ago, suddenly you’re all out of whack as he pitches you backwards, forwards, and all around the zone.
Will it hold up? That’s all we have left to wonder. He’s faced just 65 batters as of this writing, so it’s very early. His slider does rank seventh so far in baseball by Pitch Value at 4.4 Pitching Runs, so maybe he has something there that will keep getting grounders when properly paired with a fastball. Though if it was that good, you’d just think he’d look more like a poor man’s Josh Hader and get more strikeouts or swinging strikes, currently ranking 58th among relievers in the latter stat.
So there’s still question marks. For now though, Jackson has made a name for himself in Atlanta, and in the NL East. He’s letting an athletic, gifted infield do its work, and letting the Braves as a team lean on the strengths that got them to the playoffs last year. How the rest of the season plays out is the question. Right now, he’s everything the Braves need.
Merritt Rohlfing digs around stats a lot for Let’s Go Tribe and Beyond the Box Score, and does podcasting sometimes, too. Follow him on Twitter @MerrillLunch, or shoot him a compliment at firstname.lastname@example.org.