Joey Carbery and Robbie Henshaw have been omitted from Ireland's Six Nations squad but the uncapped Jamie Osborne has been included.
Carbery has been seen as the long-term successor to fly-half Johnny Sexton, who will retire after the Rugby World Cup in France this year.
There is no place for the Munster number 10 in Andy Farrell's 37-man Six Nations squad, though, as Ross Byrne and Jack Crowley were given the nod as back-ups to captain Sexton.
Centre Henshaw has endured an injury-hit season and is currently sidelined with a wrist problem, so he was overlooked by head coach Farrell.
Fellow centre Osborne, 21, is the only uncapped player in the squad as the top-ranked team in the world target a first Six Nations title in five years.
Ireland start the tournament with a trip to the Principality Stadium for Warren Gatland's first game since returning for a second spell as Wales head coach on February 4.
Farrell said: "The Six Nations is a huge competition for us and another opportunity for us to grow as a group. 2022 was a busy year as we got to work with a larger group of players as we continued to build our squad depth and competition for places.
"While there are a few players carrying knocks and others that have missed out on selection for the start of the tournament, they will have the opportunity to push their case playing for their provinces in the URC over the coming weeks as no doubt we will need to call upon the wider group as the tournament progresses."
Ireland squad:
Forwards: Ryan Baird, Finlay Bealham, Tadhg Beirne, Jack Conan, Gavin Coombes, Caelan Doris, Tadhg Furlong, Cian Healy, Iain Henderson, Rob Herring, Ronan Kelleher, Dave Kilcoyne, Joe McCarthy, Peter O'Mahony, Tom O'Toole, Andrew Porter, Cian Prendergast, James Ryan, Dan Sheehan, Josh van der Flier.
Backs: Bundee Aki, Ross Byrne, Craig Casey, Jack Crowley, Keith Earls, Jamison Gibson Park, Mack Hansen, Hugo Keenan, Jordan Larmour, James Lowe, Stuart McCloskey, Conor Murray, Jimmy O’Brien, Jamie Osborne, Garry Ringrose, Johnny Sexton (captain), Jacob Stockdale.