I had faith in Robert Stephenson heading into the 2023 season. Stephenson had one of the most effective sliders in 2022, and the Pirates had the right-handed reliever utilize the pitch far more often after being acquired by the Bucs. Stephenson did pretty well in his September stint with the Bucs, but things seem to have come crashing down for Stephenson in 2023.
The once highly-effective slider has become a much less effective offering. After holding opponents to just a .264 wOBA and 32.3% hard-hit rate, opponents have now hit it for a .337 wOBA and 47.6% hard-hit rate. The difference between a .264 wOBA and .337 wOBA is like the difference between former Pirate backup catcher Chris Stewart and former All-Star catcher Jason Vaiertek.
The diminished effectiveness of his slider has made his always-poor fastball even more of a liability. Batters are hitting .333 with a .583 slugging percentage and .415 wOBA against his four-seamer. Stephenson has consistently had one of the least effective four-seam fastballs in baseball, and with no third pitch in his arsenal, he’s been hit hard this year.
All this leads to eight earned runs allowed in just 13 innings. Of the 12 hits he’s allowed, three have been long balls. He’s walked eight batters (one intentionally) while striking out 15, which is the only silver lining in his dismal season. Stephenson has been knocked around for a 15.2% barrel rate, the 19th worst in the league.
Despite his poor numbers, the Pirates have insisted on giving Stephenson a high-leverage role. Of his 17 total appearances, 15 have come between innings 7-9 or extra innings. Before his implosion on Sunday afternoon, Stephenson allowed seven hits, including a double and a home run, along with three walks in 25 plate appearances in high-leverage situations.
Let’s just see a pitcher who has a chance to actually become a high-leverage arm. Even a promotion of Travis MacGregor, Hunter Stratton, or Carmen Mlodzinski would likely prove to be more productive than having Stephenson on the roster.
That’s not to say that a rookie should all of a sudden be handed the reins to a high-leverage role. Dauri Moreta has certiantly earned a higher volume of high-leverage innings more than anyone out of the bullpen. But replacing Stephenson for a more effective pitcher sets the bar extremely low.