O'Malley (appendectomy) was placed on the 10-day disabled list Friday.
The versatile O'Malley underwent the procedure on March 22 and his initial timetable to return was two weeks. However, the Mariners had to trim their roster down Friday with Opening Day approaching, so they will have O'Malley start the year on the DL. Taylor Motter will likely serve as the Mariners' backup shortstop while O'Malley is sidelined.