O'Callaghan comes into the second row to replace Trevor Hogan while Payne takes over at 13 with John Kelly - who played in that position against Harlequins - switching to the wing berth with Mossy Lawlor named on the bench.
Besides the change in the second row, Gaffney makes one other change up front with the experienced David Wallace named at open side flanker ahead of Denis Leamy and Alan Quinlan.
Explaining the changes Gaffney said, "Donncha was picked for the game against Llanelli but unfortunately, injury in training precluded him from taking part. So although Trevor (Hogan) has done superby well, it's a question of going with our original choice.
"The same applies to Sean who was the man in possession until injury ruled him out for the last game."
In relation to the back row, Gaffney admitted that it the area that necessitated the most deliberation. " The truth is that we have five outstanding back rows competing for three places. That might seem like a good position to be in. Of course in some ways it is, but on the other hand it's tough when quality players have to be left out.
Unfortunately we are not allowed play five back rows. For Sunday we believe we have chosen horses for courses and we must continue to do that.
C Cullen; J Kelly, S Payne, R Henderson, A Horgan; R O'Gara, P Stringer; M Horan, F Sheahan, J Hayes; D O'Callaghan, P O'Connell; J Williams, D Wallace, A Foley (capt).
Replacements: J Flannery, G McIlwham, T Hogan, A Quinlan, M Prendergast, P Burke, M Lawlor.