The Red Sox optioned Criswell to Triple-A Worcester on Friday, Chad Jennings of The Athletic reports.
Criswell put his best foot forward in competing for a rotation spot this spring, collecting a 2.95 ERA and 17:3 K:BB across 18.1 innings of work. However, Tanner Houck and Garrett Whitlock also pitched well and they were ultimately given the fourth and fifth slots. Criswell will stay stretched out in Worcester's rotation.