Ulster caretaker coach Steve Williams has brought in four players, Bryn Cunningham, Mark McCrea, Matt Miles and Justin Harrison, to a 25-man squad for the Heineken Cup tie against the Ospreys at The Liberty Stadium on Friday night.
Williams said: "Again like everything else we have to pick the team for the different oppositions and the challenges that they will present. We need to be streetwise against the Ospreys and we are well aware of the threats that they bring to the game."
Ulster Rugby have currently three back row players Stephen Ferris, Neil McMillan and Roger Wilson and out-half David Humphreys unavailable due to injury.
ULSTER SQUAD (v Ospreys):
Backs: M Bartholomeusz; S Danielli, B Cunningham, M McCrea, T Bowe, A Trimble, R Dewey, P Steinmetz, N O'Connor, P Wallace, I Boss, K Campbell;
Forwards: J Fitzpatrick; B Young, D Fitzpatrick, M Miles, R Best, N Brady, J Harrison, R Caldwell, C Del Fava, M McCullough, N Best, K Dawson, D Pollock.