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Red Sox reliever Justin Slaten delivered a scoreless rehab outing with Double-A Portland as Boston monitors the right-hander’s return from an oblique strain ahead of the Tigers series finale.

The Boston Red Sox received a major update on reliever Justin Slaten before Wednesday’s series finale against the Detroit Tigers, as the right-hander turned in an impressive rehab appearance after nearly a month on the injured list.

Slaten, sidelined since April 8 with an oblique strain, delivered a scoreless inning with two strikeouts for Double-A Portland on Sunday, potentially putting the key bullpen arm on track for a return to Boston on an accelerated schedule.

The Portland numbers were encouraging on their own, but what Slaten said afterward made the story more compelling. He told reporters he was genuinely caught off guard by what he had in his arm — a 96-97 mph fastball and a 92-93 mph cutter at an 11 a.m. rehab start. That velocity, he said, exceeded his own expectations, according to The Boston Globe‘s Alex Speier.

Slaten Rehab Outing Stuns Even the Pitcher Himself

“Shocked” was the word Slaten used to characterize his velocity numbers, as quoted by Speier. The 28-year-old righty declared himself physically ready for activation but deferred to the organization on when that would actually happen.

His next hurdle is a scheduled Triple-A Worcester appearance on Wednesday, the same day as the Tigers series finale, CBS Sports reported.

“He’s ready to go,” said Worcester interim manager Iggy Suarez, as quoted by Patrick McAvoy of Sports Illustrated. “To have a guy like that get back to health and get him up in the big leagues is what we want to do.”

Red Sox Need Slaten As Soon as Possible

Slaten had not surrendered a run across his first four appearances of 2026 before going on the IL, striking out five while walking just two. He posted a 2.93 ERA across 44 appearances as a rookie in 2024. Getting that arm back at 96-plus mph is a necessity for a 15-21 club still trying to gain ground in the AL East.

At the same time, the back of the Red Sox bullpen with Garrett Whitlock in the eighth inning setting up closer Aroldis Chapman has not been the same lockdown combination that the Red Sox saw last year, especially in the second half of the 2025 season.

Whitlock allowed only one earned run in 26 2/3 innings after the All-Star break, Chapman only three in 23 1/3 innings.

This year, Whitlock has already allowed six earned runs in 14 1/3 innings. Chapman has been more solid, allowing just one in 11 2/3, but has shown a worrying drop in his fastball velocity.

Boston’s starting rotation has been battered by injuries throughout the early weeks of the season, with Garrett Crochet and Sonny Gray both spending time on the injured list, putting additional pressure on the bullpen arms. Gray — who exited a late-April start against Detroit with hamstring soreness — could potentially return as early as Wednesday’s finale as well, according to Kate Manganelli of BoSox Injection.

Slaten arriving back in Boston at full velocity would make a big difference for the Red Sox as they try to recover from a turbulent 15-21 start. Wednesday’s Worcester outing for Slaten will go a long way toward answering which version the Red Sox are getting back.