JUSTIN Tipuric will miss the Ospreys's visit to Rodney Parade on Monday.
The flanker, so impressive in the defeat of the Scarlets on Boxing Day, is sidelined with a shoulder injury.
Sam Lewis fills in at No. 7 in his absence, alongside Joe Bearman and Ryan Jones in the back row.
Forwards coach Jonathan Humphreys said: "This period of three games in nine days is crucial for us and having won the first game against the Scarlets, it really is vital that we keep on working hard as a group, looking to improve and to find the performance level that will get us into the play-off spots before the Pro12 goes into a break for Europe and the LV.
"As a coaching group, we've got to be pleased with the win against the Scarlets, but there's still room for improvement.
"We showed great effort and commitment, good discipline and we played the game plan well but there were areas of the performance where we could have done better.
"With the quick turnaround and the nature of Christmas rugby, there's not much time to prepare for this game but what time we have got will be used to ensure the boys are focused and know what is needed to raise the performance another level again."
Ospreys: R. Fussell; R. Jones, T. Isaacs, A. Bishop, E. Walker; D. Biggar, K. Fotuali'i (capt); R. Bevington, R. Hibbard, A. Jones, L. Peers, J. King, R. Jones, J. Bearman, S. Lewis. Reps: S. Baldwin, D. Jones, C. Griffiths, J. Thomas, M. Allen, R. Webb/T. Habberfield, M. Morgan, A. Beck.