Hisashi Iwakuma is making progress in recovery from right shoulder surgery and could be back in the Seattle Mariners pitching lineup as early as mid-May, the club's manager Scott Servais said Tuesday.

Speaking to reporters at the annual baseball winter meetings, Servais said Iwakuma is a "huge asset" to the team, and his return could "probably" happen in mid-May to early June.

The 36-year-old Japanese right-hander underwent surgery in late September after an injury-shortened season for the Mariners. He went 0-2 with a 4.35 ERA in six starts, failing to record a win for the first time in his major league career.

In late November, Iwakuma signed a minor-league contract with the Mariners with a spring training invite, after the club declined its 2018 option on the veteran.