Howard is listed as the Guardians' scheduled starter for Thursday's game against the Tigers in Detroit.
For what will be his Guardians debut, Howard will step into the rotation spot vacated by Logan Allen, who was optioned to Triple-A Columbus on Sunday. Prior to being acquired from the Giants last Friday, Howard had accrued a 5.63 ERA, 1.83 WHIP and 21:11 K:BB across 24 innings in seven appearances (two starts) at the big-league level.