Criswell was called up to serve as the 27th man for Saturday's doubleheader against the Angels.
Criswell has bounced between a long-relief role in the majors and a rotation spot with Triple-A Durham throughout the year. None of his eight MLB appearances have been starts, but he's averaged 3.5 innings per appearance. His 4.82 ERA and 1.46 WHIP mean he's unlikely to move into a higher-leverage role any time soon.