Perez has been out since late June, when he left a game against the Los Angeles Angels with a left thumb injury that also had caused him to miss time earlier in the season.
He ended up having surgery on the thumb, with manager Mike Matheny saying at the time he'd likely need eight weeks to recover. It wasn't immediately clear how many rehab games Perez would need before joining the Royals.
"He's been going about it pretty hard here for a while,'' Matheny said Monday. "Watching everything he's doing, he feels right.''
A seven-time All-Star, Perez was hitting a career-worst .211 with 11 home runs a year after leading the majors with 48 homers and 121 RBIs in 2021.