The sinker isn’t Archer’s only problematic pitch, but it is his newest one. His four-seamer has resulted in a .380 wOBA this season, which is obviously suboptimal, but it’s also pretty much in line with the .372 wOBA it resulted in during the 2017 season, when he was a 4.5 WAR pitcher. And his slider — easily his best pitch throughout his career — has held up pretty well, holding opposing hitters to a .292 wOBA and generating more whiffs than at any point in his career. Archer can succeed with one bad fastball, even when he’s throwing it nearly half the time the way he did two years ago. It’s adding a second, even worse fastball to the mix that has seemed to unravel his game.
Archer’s sinker isn’t exactly new, per se. He threw a good number of them from 2012-14, and in fact, he was pretty successful with the pitch. In 2014, he limited opponents to a .258/.342/.333 line with the pitch, relying upon it as his primary weapon (41% of all pitches thrown). But the next year, he ditched it, opting to focus on his four-seamer, his slider, and his changeup. It remained that way until he was traded at the deadline last year to the Pirates, an organization who has dug its heels in on focusing on a two-seamer, get-ground-balls approach while the rest of baseball has shifted to a four-seam, strike-guys-out mentality.