I like Wolf the best. He is pitching for the Dodgers and has the best K/9 ratio of the group. Wolf has a good defense behind him and a pretty good offense to back him up. Even without Manny, I still think Wolf is the best option, probably best bullpen to get him Wins too.
Next would probably be Snell. He pitches for a poor team, but Snell has better stuff and potential than Washburn. Washburn had been good to start, but he rarely ever has kept the pace up. He will eventually burn whoever has him. I wouldn't want Washburn.
Richmond and Cecil are relatively unknowns to me. I foresee a big roller coaster ride with these guys, I'd stay away.
None of these SP are totally safe options, but I like Randy Wolf from these choices.