Moore was not on the 40-man roster, so right-hander Tyler Cloyd was designated for assignment to open a spot for the 23-year-old from Oregon State.
Moore, the Mariners' No. 4-ranked prospect per MLBPipeline.com, has gone 3-1 with a 3.19 ERA in eight starts for Tacoma and was 1-2 with a 2.08 ERA in six outings (five starts) with Double-A Arkansas to open the season.
Moore was selected by Seattle with a Competitive Balance Round B selection, the 72nd overall pick, in the 2015 Draft and has moved quickly through the Mariners' system. He was the club's Minor League Pitcher of the Year last year after going 12-4 with a 2.