The Red Sox optioned Criswell to Triple-A Worcester on Saturday, Jen McCaffrey of The Athletic reports.
After joining the rotation in mid-August as a replacement for James Paxton (calf) and covering at least three innings in each of his six ensuing outings, Criswell had worked out of the bullpen for his last two appearances, giving up a total of three runs (two earned) over two innings. With Richard Fitts overtaking him as the Red Sox's No. 5 starter and with Luis Garcia (elbow) returning from the injured list, Criswell will end up as an odd man out on the 28-man active roster. The 28-year-old righty owns a 4.08 ERA and 1.35 WHIP across 99.1 innings with the Red Sox on the season.