Yamamoto was optioned to the Marlins' alternate training site Friday, Jordan McPherson of the Miami Herald reports.
Yamamoto was initially presumed to be the No. 5 starter heading into the regular season, but his move to the team's alternate training site in Jupiter likely signals that Elieser Hernandez will occupy the final spot in the starting rotation. Yamamoto should be one of the team's top options to fill in as a starter if injuries occur in the rotation this year. The 24-year-old posted a 4.46 ERA and 1.14 WHIP over 78.2 innings in 15 starts with the Marlins in 2019.