Iwakuma reported that he felt additional soreness in his back after a throwing session on Friday, according to the report, which led to the move.
The Mariners placed Iwakuma on the disabled list on April 24 with a strained right latissmus dorsi. He has not pitched since then.
Mariners manager Lloyd McClendon previously expressed optimism that Iwakuma would bounce back from two mediocre starts at the beginning of the season.
But he told MLB.com Friday that Iwakuma is not progressing in his rehab as well as he had hoped he would.
McClendon says Hisashi Isakuma not responding as well as hoped on Dl with lat strain. Will be shut down from throwing next 10-14 days.— Greg Johns (@GregJohnsMLB) May 12, 2015
Iwakuma last played catch on Friday. He says injured lat muscle still sore at that point, so revisited doc and decision made to shut down.— Greg Johns (@GregJohnsMLB) May 12, 2015
During his last start on April 20, Iwakuma felt shoulder fatigue, general manager Jeff Zduriencik said.
Iwakuma struggled in his first three starts of the 2015 season, going 0–1 and posting a 6.61 ERA.
The 34 year old pitcher is in the final year of a three-year, $20 million contract with the Mariners.