Darwinzon Hernandez is effectively wild

Pitchers can find success in a variety of ways. While the most common route to that in today’s game is getting a plethora of strikeouts, there are a few that succeed by inducing soft contact, getting ground balls, and controlling the ball. As obvious conventional wisdom goes, if you walk a lot of hitters, the harder it’ll be to find success. You’re already at a point where you need to combat those walks with strikeouts, avoiding the BABIP threat. In an era with tons of home runs, you run the risk of making those extra base runners inflate your ERA.

There is one pitcher going against a lot of that conventional wisdom though. His name is Darwinzon Hernandez, a rookie reliever for the Red Sox. To put it simply, Hernandez’s numbers would indicate that he’s… effectively wild. For his minor league career, the bulky left-hander struck out 10.3 batters and walked 5.5 batters per nine innings. But through his high strikeout and ground ball rates, he was able to keep the run prevention under control, posting a 3.40 ERA.

Though he pitched as a starter for most of his minor league career, his relief prospects were always high due to his lethal fastball/curveball combo. According to Fangraphs’ Eric Longenhagen:

We do not think Hernandez is a long-term starter and instead think he’ll be an elite bullpen arm. His fastball often sits in the upper-90s when he’s starting so it should at least stay there if he’s moved to relief and, though his feel for it comes and goes, his curveball can be untouchable at times. Maybe the strong early-season performances of Matt Barnes, Brandon Workman, and Ryan Brasier has stifled some of the disquiet about the Red Sox bullpen, but in the event that they need an impact arm, I think it’s more likely to be Hernandez than a piece outside the org. Some of this is due to the quality of the farm system, but Hernandez might also just be better than a lot of the options that will eventually be on the trade market.

After two brief stints with the Red Sox major league staff in April and June, he was called up for good to pitch out of the big league bullpen after the All-Star break. Since then, he’s been fantastic, putting up a 2.42 ERA and 2.01 FIP in 22 13 innings, striking out 42 batters and walking 16.

Among 498 pitchers with at least 20 innings this season, only eight have a higher walk rate than Hernandez and only five have a higher strikeout rate. Out of that same group of pitchers, not one has posted a higher rate of plate appearances ending in a strikeout or walk.

Darwinzon Hernandez doesn’t allow many batted balls

Name Team K% BB% K+BB%
Name Team K% BB% K+BB%
Darwinzon Hernandez Red Sox 40.8 16.9 57.7
Austin Adams Nationals/Mariners 43.7 13.6 57.3
Josh Hader Brewers 47.5 7.0 54.5
Tanner Rainey Nationals 34.6 18.8 53.4
Joshua James Astros 36.9 14.7 51.6
Matt Barnes Red Sox 39.7 11.8 51.5
Brandon Workman Red Sox 35.7 15.5 51.2
Ken Giles Blue Jays 41.2 8.5 49.7
Jose Quijada Marlins 29.9 19.7 49.6
Nick Anderson Marlins/Rays 41.5 7.0 48.5

Minimum 20 IP FanGraphs

Five of the seven pitchers that have a higher walk rate than Hernandez have an ERA over five. Of those pitchers, the one with an ERA closest to his mark of 2.93 is Tanner Rainey at 4.17. A big factor in this is obviously the high strikeout rate, but another factor would be that Hernandez is one of three pitchers in baseball this season that hasn’t allowed a home run (minimum 20 innings).

Hernandez’s batted ball metrics are terrific. His average exit velocity against is far below the major league average, sitting at 85.1 miles per hour. Out of the 52 batted balls that he has allowed, not one has been classified as a barrel. He’s also induced a single digit launch angle, contributing to his above-average ground ball rate.

Hernandez has been very good when it comes to preventing damage on contact (xwOBAcon ranks in the top three percent of baseball), but luck has not been on his side (wOBAcon ranks in the bottom 20 percent), so it’s quite possible that his already good ERA is being inflated by bad luck.

Baseball Savant

Hernandez is currently defying the norms that are associated with high walk rates. If he continues his above-average skills at preventing contact and limiting good contact, there’s no reason to believe that this can’t continue. Over his last six outings, he’s improved his walk numbers (14.8 percent) and has posted a 0.00 ERA and 0.69 FIP in that time. With some of the best raw stuff in the game, if he could even just improve his control at a slight degree, he’ll have the makings of one of the better relievers in baseball.


Patrick Brennan loves to research pitchers and minor leaguers with data. You can find additional work of his at Royals Review and Royals Farm Report. You can also find him on Twitter @paintingcorner.

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