Neither if those are the only two SS you have. I would play Rut while he his hot and keep Rollins for the stretch. There is no telling what kind of playing time Rut will get once Tulo comes back (unless they move him). Besides, Rollins has been a good source of SBs and has hit for decent power as well and Rut is a rookie that may not keep up the current hot streak once pitchers get used to him (or even start pitching around him because of the Rockies currently terrible offense). If you need to lose someone, work out a trade. Don't just give them away free to the wire.