Gilbert was promoted from High-A Modesto to Double-A Arkansas on Monday, Modesto radio broadcaster Keaton Gillogly reports.
Gilbert will be joined in Arkansas by two of the Mariners' other more highly regarded prospects in right-hander Ljay Newsome and catcher Cal Raleigh. The 22-year-old Gilbert, who began the season in the South Atlantic League before making the jump to High-A, turned in a 1.73 ERA and 1.03 WHIP over his 12 starts with Modesto.