Yamamoto will be called up from Double-A Jacksonville to start Wednesday's game against the Cardinals, Joe Frisaro of MLB.com reports.
Yamamoto will make his major-league debut Wednesday with Jose Urena heading to the injured list with an lower-back tightness. The 23-year-old was optioned to the minors after failing to make the Opening Day roster out of spring training, and went on to post a 3.58 ERA, 1.20 WHIP and 64:25 K:BB over 12 starts with Double-A Jacksonville.