Leinster will be without their skipper Johnny Sexton and their world-class front row Tadhg Furlong for their Champions Cup opener against Racing 92 .
Garry Ringrose leads the team while Jason Jenkins and Charlie Ngatai - who brings his Top 14 experience from Lyon - make their Champions Cup bows for Leinster. Jamie Osborne may do so off the bench.
For Ross Byrne, Ireland's goalkicking saviour against Australia three weeks ago, this is a golden opportunity to show Andy Farrell he deserves another go during the Six Nations.
Byrne has guided the province to victory in France before, notably in the 2020 trip to Montpellier, though was at the helm from the start for the semi-final loss at La Rochelle in May 2021. He will be partnered in the half-back line by Jamison Gibson-Park.
LEINSTER: Keenan, O'Brien, Ringrose, Ngatai, Lowe, R Byrne, Gibson-Park; Porter, Sheehan, Ala'alatoa, Ryan, Jenkins, Baird, van der Flier, Doris.
Replacements: Kelleher, E Byrne, Healy, Molony, Conan, McGrath, H Byrne, Osborne.
Mike Haley comes into the Munster lineup for the visit of Toulouse to Thomond Park on Sunday.
But the match has come too quick for Conor Murray after his return to full training this week following a calf injury. The scrum-half is not included in the matchday squad.
Haley returns to the fold after missing last weekend's bonus-point victory over Edinburgh due to return-to-play protocols following a concussion.
The full-back's inclusion is the only change from that side, while they also will have the services of Keith Earls to call on from the bench.
Earls is set to make his first appearance since September.
MUNSTER: Mike Haley; Calvin Nash, Antoine Frisch, Rory Scannell, Shane Daly; Joey Carbery, Craig Casey; Jeremy Loughman, Niall Scannell, John Ryan; Jean Kleyn, Tadhg Beirne; Peter O’Mahony (capt), John Hodnett, Gavin Coombes.
Replacements: Diarmuid Barron, Josh Wycherley, Roman Salanoa, Jack O’Donoghue, Alex Kendellen, Paddy Patterson, Jack Crowley, Keith Earls.
Ulster will be without experienced pair Iain Henderson and John Cooney for their trip to Sale on Sunday.
Henderson and Cooney are both ruled out with head injuries sustained in a 38-29 defeat to Leinster last weekend.
Cooney is replaced by Nathan Doak at scrum-half, while Matty Rea takes Henderson's place in the back row.
Jacob Stockdale will start on the left wing for the province, with Stewart Moore dropping to the bench.
Stockdale is joined in the backfield by Mike Lowry and Ethan McIlroy, while Stuart McCloskey and James Hume team up in midfield.
ULSTER: Mike Lowry; Ethan McIlroy, James Hume, Stuart McCloskey, Jacob Stockdale; Billy Burns, Nathan Doak; Andy Warwick, Rob Herring, Tom O'Toole; Alan O’Connor (captain), Kieran Treadwell; Matty Rea, Nick Timoney, Duane Vermeulen.
Replacements: Tom Stewart, Eric O’Sullivan, Marty Moore, Sam Carter, Marcus Rea, Dave Shanahan, Stewart Moore, Ben Moxham.
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