Edwin Jackson vs. Matt Riley or Jerome Williams

[coolarmadillo]

I've got Jackson on my team as my 6th starter and I've heard he may go down for a while. Riley and Williams are available. Riley's been given the #4 spot and had a good spring and Williams may be sent down soon. Should I hang on to Jackson or pick up Riley or Williams? Riley makes the most sense short term, but should I be thinking long term? If so, who do you like for the season of these three? Roster below:

12-team league
24 man rosters
5x5 + holds and slugging

Roster:
C: V. Martinez
1B: M. Sweeney
2B: A. Kennedy (J. Reyes when eligible and healthy)
3B: A. Ramirez
SS: A. Rodriguez
OF: M. Ordonez
OF: B. Abreu
OF: S. Green
Util: R. Klesko (J. Reyes at times if healthy until eligible at 2B)
Bench: J. Reyes
Bench: A. Sanchez
Bench: P. Konerko

SP: T. Hudson
SP: J. Santana
RP: T. Hoffman
RP: A. Benitez
P: B. Koch
P: D. Kolb
P: C. Bradford
Bench: R. Soriano (until healthy)
Bench: V. Padilla
Bench: O. Perez
Bench: A. Eaton
Bench: E. Jackson