Munster have named an unchanged team for Sunday's crucial Pool 4 game against Castres at Thomond Park.
Peter O'Mahony was doubtful, but has shaken off an ankle injury to captain the side.
Niall Scannell has also given the province a boost, returning from a rib injury to take his place on the bench.
Munster know a win against the French side will see them into the quarter finals.
Team named for Sunday's #MUNvCO
— Munster Rugby (@Munsterrugby) January 19, 2018
Ulster must also win against Wasps to guarantee their place in the last eight.
They make three changes to their side for the trip to the Ricoh Arena.
Darren Cave comes in for the injured Craig Gilroy, with Louis Ludik switching out to the wing.
Two changes come in the pack; Kyle McCall replaces Callum Black at loosehead, while Kieran Treadwell starts in the second row, with Matty Rea dropping out, and Iain Henderson switching to the backrow.
Here is your Ulster team for Sunday’s crunch European Champions Cup tie away to Wasps ðŸ‘‡
— Ulster Rugby (@UlsterRugby) January 19, 2018
Joey Carbery makes his return to the Leinster bench for their dead rubber agaist Montpellier.
They make six personnel changes, three in the pack, and three in the backs.
Up front, Cian Healy, James Ryan and Dan Leavy replace Jack McGrath, Scott Fardy and Jordi Murphy.
Jamison Gibson-Park, Ross Byrne and Rob Kearney all come into the backline. Gibson-Park is in for Luke McGrath, while Byrne takes Johnny Sexton's place in the 10 shirt.
Sexton isn't included in the squad, but Leinster say he is fully fit.
The other change sees Rob Kearney replacing Fergus McFadden. Kearney starts at fullback, with Jordan Larmour shifting to the wing.
— Leinster Rugby (@leinsterrugby) January 19, 2018
Connacht include Ultan Dillane, Kieran Marmion, Quinn Roux and Bundee Aki in their side to play French side Oyonnax.
Matt Healy is named on the wing, for his 100th Connacht appearance.
Kieran Keane's side are already guaranteed a place in the quarter finals.
— Connacht Rugby (@connachtrugby) January 19, 2018