Fletcher will be part of the Mariners' 60-man training roster.

The 24-year-old southpaw is not on the 40-man roster, but he could have made his MLB debut under normal circumstances after finishing last season with a strong run at Double-A. He had a 2.09 ERA, 0.93 WHIP and 84:18 K:BB in 73.1 innings as a reliever across three levels of the minors in 2019.