Liam Hendriks is dominating with the fastball

The 2018 Athletics thrived with an extremely reliable bullpen. They were led by the breakout of Blake Treinen, who had previously been a middling reliever before turning in one of the most dominant seasons of the last decade.

The 2019 A’s have survived with a moderately reliable bullpen, led by the breakout of Liam Hendriks. Hendriks had also been a middling reliever before turning in one of the most dominant seasons of the last decade.

Hendriks has certainly had an interesting journey the past two seasons. On June 25, 2018, Hendriks was designated for assignment. No one wanted to give a roster spot to a matcher with 7.36 ERA, so he cleared waivers and accepted the assignment to Triple-A Nashville. Hendriks didn’t return to the major league roster until September 1st. Over the last month, he has posted a 1.38 ERA and earned enough trust to open the American League Wild Card game in New York.

During his time in Triple-A, Hendriks fixed a mechanical flaw, gaining velocity in the process. Before his time in Nashville, Hendriks sat ~92-93 MPH with the four seamer, when he returned to the Majors, he was consistently hitting 96 mph with ease.

This year, Hendriks is leading relievers in fWAR at 3.1 and ERA at 1.21 (his ERA on the season is 1.43 when including his two appearances as an opener which would rank him second behind Kirby Yates). He doesn’t rank as highly in advanced run estimators; he ranks 12^th in SIERA and 9^th in strikeout minus walk rate for instance. Regardless, he’s having an excellent year for any reliever, especially one who was DFA’d and passed up just over a year ago.

Hendriks, like so many others, found success by ditching the sinker, which for the early part of his career, was his primary fastball. Like many others in today’s game, he adjusted away from the sinkerball, and in 2016, he began throwing the four seamer more often. In 2017, and 2018, he ditched the sinker more often replacing the secondary offering with a slider.

This year, he’s all but abandoned the pitch, along with a rarely-used changeup.

Baseball Savant

Hendriks didn’t have poor results with the sinker last year. Per Baseball Savant, hitters whiffed at 18.9 percent of the sinkers they swung at and produced a .229 xwOBA against the pitch. Both of those marks were better than his overall numbers against the four seamer.

The sinker didn’t fit into Hendriks’ new game plan. With his newfound velocity and nearly 100 extra rpm of spin, Hendriks is throwing more fastballs at the top of the zone. High spin fastballs resist gravity better and stay off a hitter’s swing plane more effectively. When thrown at the letters, that effect is amplified.

Hendriks’ fastball has a 29.9 whiff percentage this year, an 11.9 point jump from last season and the highest mark of his career. With his fastball taking on new life, he hasn’t needed to throw the sinker which is a slower pitch that doesn’t stay off the bat plane as well.

Hendriks has benefited from some major luck this year. Despite a 50.7 fly ball rate in record-setting year for home runs, Hendriks has only allowed two balls to leave the yard. A 2.6 HR/FB percentage isn’t sustainable unless Hendriks has cracked the dinger code.

Even if Hendriks were giving up a normal amount of homers, this would still be an impressive season. This has been one hell of a bounce back. When he was designated for assignment last year, it made sense that no one took him. In hindsight, Hendriks has made every team look mighty foolish.

Kenny Kelly is a writer for Beyond the Box Score and McCovey Chronicles. You can follow him on Twitter @KennyKellyWords.