I would rather have Rock take on Taker, Brock or Orton, but since the former two are going to feud with each other come Mania and the latter is tossed aside, I guess Cena is the best option. If Rock has to job to a full-timer that's not from the AE, then Cena is the best option aside from Orton. (I don't care about the "young guys", they aren't credible enough to even face The Rock)
I've been waiting a while to seeing the Undertaker teach Cena a lesson at Mania, cuz Cena just never loses cleanly I think the only time he lost cleanly was to The Rock at Mania
Not at all. It's not even his lone clean job at Mania. He was pinned clean by Randy Orton at WM24 in the triple threat also involving HHH.