soxprospects.com now projects Criswell to be on the 26 man roster as the 6th SP'er.
Here are their projected rotations at the minor league levels (many have 6 listed)
AAA: Murphy, Walter, Fitts, Gambrell, Van Belle
AA: Wikelman, Dobbins, Bastardo, I Coffey, Penrod, Song
A+: Perales, Sandlin, Monegro, E R-C, Rogers, Duffy
A-: Early, Judice, Soto, Cohen, F Hernandez, Mullins
FCL: Polanco, Batista, Balderas, Lee, Yonfi Rodriguez