In an unexpected yet intriguing move, the Seattle Mariners have brought former Oakland A’s reliever Will Klein back into the fold, signaling their belief that the hard-throwing righty could still unlock his potential. Klein’s journey to this point has been a mix of highs and lows, but the Mariners’ track record of developing pitching talent could be just what he needs to turn the corner.
Klein’s story began with a midseason trade last year, when the Athletics dealt Lucas Erceg to the Kansas City Royals for a package that included right-handed starter Mason Barnett, reliever Will Klein, and outfielder Jared Dickey. Klein made his big-league debut with the Royals on April 28 before being shipped to Oakland, where his first two outings were promising. He logged 1.1 innings with a walk and a strikeout, showing the kind of raw stuff that intrigued scouts.
However, things went south in his third appearance, when he gave up five earned runs in just one-third of an inning against the New York Mets. The A’s quickly sent him down to Triple-A Las Vegas, where he struggled with a 5.06 ERA over 5.1 innings. Though his performance was underwhelming, Klein’s raw talent—particularly his fastball—was never in question. The real issue was control.
In January, the Mariners acquired Klein for cash considerations, a move that immediately turned heads. Given Seattle’s remarkable ability to develop pitchers into reliable late-inning options, many wondered if they could tap into Klein’s upside. While he didn’t make the Mariners’ Opening Day roster, the team has now recalled him to the 26-man roster, opting to send right-hander Gregory Santos down. Santos had posted a 5.14 ERA and a concerning 2.29 WHIP across seven innings.
Klein’s minor league numbers this season haven’t been pretty. He’s posted a troubling 12.79 ERA and has walked 19.4% of batters faced in just 6.1 innings. But his FIP of 3.37 suggests that his performance is better than his numbers imply. Klein’s strikeout rate of 36.1% is the highest it’s been since 2021, and his stuff is showing signs of improvement. In his most recent outing on April 15, his four-seam fastball touched 98.6 mph, and his slider velocity jumped to 87.6 mph, showing noticeable gains from last season.