Seattle Mariners pitcher Hisashi Iwakuma is expected to miss four to six weeks because of inflammation in his right shoulder, the team announced.

Iwakuma was placed on the 10-day disabled list Wednesday and underwent testing Friday in Seattle. The Mariners' medical director, E. Edward Khalfayan, confirmed the initial diagnosis of shoulder inflammation.

Iwakuma, 36, is 0-2 with a 4.35 ERA in six starts this season, his sixth with the Mariners.