Non-pitching hand. Sounds painful, but I’d go with over-work and Covid as the reasons for his struggles. Hopefully he’s a useful piece again next year. This season, not so much…This may be why Barnes has struggled as of late
https://www.bostonglobe.com/2021/10/16/sports/red-sox-reliever-matt-barnes-anything-that-could-go-wrong-did-go-wrong-last-six-weeks/
Matt Barnes recently sliced off the tip of his left thumb while chopping a pepper.