I think the best way to handle Jeter is to try to zero in on games played/AB's to help with projections/rankings.
Right now, I am projecting 485 AB's, as I want to see that he'll be ready for opening day before I bump it up, and even then, I believe he'll require a little more rest between recovery and age. I have him as my 14th best SS in mixed 12 team MI CI 5 OF leagues. He'll approach double digit homers, have decent counting stats even with limited playing time (74 runs, 60 rbi) and still provide solid BA .303+
As far as Rivera goes, I am not too concerned considering what the injury was and the time he will have to heal. I currently have Rivera as my 8th best closer, but that's with Rodney and Nathan ahead of him. It's an area I could see changing.
Twitter: @dmojr - Always available to talk fantasy or be that second opinion before a trade.