Ireland coach Joe Schmidt gave a positive update on Johnny Sexton's fitness when naming his squad for the opening two rounds of the Six Nations.
Sexton, the reigning World Player of the Year, has been troubled by a knee tendon issue and will miss Leinster's final European Champions Cup pool match at Wasps on Sunday.
"Johnny Sexton is making good progress, while Joey Carbery and Jack Carty have both performed consistently well so far this season," Schmidt told www.irishrugby.ie after naming a 38-man squad.
"Ross Byrne is unlucky in an incredibly tight call.
"He is still definitely in our thinking and will continue to press for inclusion through the Six Nations and beyond, while Billy Burns has also fitted in really well for Ulster this season."
Scrum-half Luke McGrath is likely to miss the entire competition after damaging knee ligaments, but Conor Murray is back after a neck injury.
With Kieran Marmion also missing through injury, Ulster's John Cooney and Connacht's uncapped Caolin Blade offer scrum-half options.
On the centres and back-three positions, Schmidt added: "Bundee Aki and a fresh and fully fit Robbie Henshaw squeeze out Rory Scannell, who was great for Munster last Friday, and Stu McCloskey, who continues to give Ulster gain line as well as defensive solidity.
"At outside centre Tom Farrell has forced his way into contention and Chris Farrell is working his way back to match fitness, improving week by week.
"We're sure that Sam Arnold and Rory O'Loughlin will continue to improve and both have plenty of promise.
"Adam Byrne and Dave Kearney were both very good against Toulouse.
"The Connacht outside backs have been consistently good; Mike Haley is growing into his role with Munster while we look forward to a fit again Darren Sweetnam gaining some game minutes over the coming weeks."
Finlay Bealham, Marty Moore, Stephen Archer and Rob Herring are among the forwards to miss out.
"It's been great to watch the provincial teams doing so well in recent weeks," Schmidt said. "There have been a number of tight calls across almost every position."
Ireland start their Six Nations campaign at home to England on February 2 before meeting Scotland at Murrayfield seven days later.
— Irish Rugby (@IrishRugby) January 16, 2019
Ireland squad for Six Nations
Backs: Will Addison (Ulster), Bundee Aki (Connacht), Caolin Blade (Connacht)*, Joey Carbery (Munster), Jack Carty (Connacht)*, Andrew Conway (Munster), John Cooney (Ulster), Keith Earls (Munster), Chris Farrell (Munster), Tom Farrell (Connacht)*, Robbie Henshaw (Leinster), Rob Kearney (Leinster), Jordan Larmour (Leinster), Conor Murray (Munster), Garry Ringrose (Leinster), Jonathan Sexton (Leinster), Jacob Stockdale (Ulster)
Forwards: Rory Best (Captain, Ulster), Tadhg Beirne (Munster), Jack Conan (Leinster), Sean Cronin (Leinster), Ultan Dillane (Connacht), Tadhg Furlong (Leinster), Cian Healy (Leinster), Iain Henderson (Ulster), Dave Kilcoyne (Munster), Jack McGrath (Leinster), Jordi Murphy (Ulster), Sean O'Brien (Leinster), Peter O'Mahony (Munster), Andrew Porter (Leinster), Rhys Ruddock (Leinster), James Ryan (Leinster), John Ryan (Munster), Niall Scannell (Munster), CJ Stander (Munster), Devin Toner (Leinster), Josh van der Flier (Leinster)
* Denotes uncapped player