Hisashi Iwakuma recently announced that he would be heading to Japan to try and continue pitching. The 37-year-old has been oft-injured since the start of 2017. He made six starts, and that sixth start would be the last time he took the mound for the Mariners. Shoulder injuries derailed him from there.
Up until the shoulder injuries, Iwakuma was a highly underrated pitcher for the Mariners. From 2012-2017, he went 63-39 over 136 starts and 150 total appearances. The ERA was great as well, coming in at 3.42. The first four years were even better, coming in at 3.