Iain Henderson is on standby to take over from Ryan, who is a doubt for the game at the Stade de France in Paris due to a wrist injury.
If Henderson is named in the starting XV, his place on the bench is likely to go to Ryan’s Leinster team-mate Joe McCarthy, although Ryan Baird would also be in the mix.
If Ryan misses out, it will likely mean there will be two changes in the front five of the pack, with Dan Sheehan set to come in for his first start of the World Cup after coming off the bench in the win over South Africa. Rob Herring is in line to be named ahead of Rónan Kelleher on the bench.
Jack Conan is also in line to be named among the replacements for the game, where Ireland will be led out by Peter O’Mahony on his 100th cap for Ireland. Robbie Henshaw is set to miss the game due to an unspecified niggle.
“Robbie has a bit of a niggle and we’re finding out about that today,” confirmed forwards coach Paul O’Connell after the team’s final training session on Wednesday at their base in Tours before moving on to Paris.
“I’m sure there’ll be some information on that tomorrow,” added O’Connell.
The 30-year-old Leinster and Ireland centre would likely have been among the replacements again given the form of Bundee Aki and Garry Ringrose, although he did provide real energy off the bench in Ireland’s last two games against Tonga and South Africa.
Stuart McCloskey, Keith Earls and Jimmy O’Brien are all now vying for the number 23 shirt, and given their game profile in the warm-ups and at this World Cup (Earls played an hour against Romania, whereas McCloskey and O’Brien have yet to play a minute) the Munster man looks the likelier option.
Henshaw had previously been ruled out of the pool opener against Romania with what was understood to be a slight hamstring issue. But a recurrence of that problem might even place a cloud over his continuing participation in the tournament should Ireland progress of course.
Were Scotland to win by more than seven points, or if both teams registered a bonus point and Scotland won by a margin between six and 20 points, they would go through to the quarter-finals at Ireland’s expense and O’Connell agreed that this is effectively a knock-out game.
“Yeah, I just had that conversation with the doctor today. That’s exactly what it is now this weekend really for us. We’re aware of the permutations but the focus is really on winning.”
Ireland have fallen short unexpectedly at previous World Cups when expectations had turned to possible match-ups or prizes further down the line, but one of the keys to this team winning their last 16 Tests has been not to look beyond the game immediately in front of them.
“I think that’s one of the things the lads are really good at, they’re really good at staying focused on the next game and not looking beyond it,” said O’Connell.
“They kind of acknowledge whenever we’ve been on tour down in New Zealand or whenever we’re playing in the Six Nations, in terms of having a chance of winning it. They might have a quick chat about it, and that allows them to focus on what’s in front of them.
“Staying focused on this game and absolutely nothing else is a skillset they’ve gotten really good at.
“Then we’ve just got to get better,” added O’Connell. “There’s a lot of things that we were excellent at against South Africa but there’s a lot of things we can improve on in terms of our attack, in terms of our defence, in terms of ruck, lineout obviously.
“There’s always bits to get better at and that’s what I think sometimes helps the lads kind of tune out the noise a little bit of what might happen after the game. They enjoy focusing on the bits and pieces that help them be better and they can ignore the bigger picture of the game at the weekend.”
Ireland lost five of their first eight lineouts against South Africa but thereafter problem solved so effectively that they won 12 of their ensuing 14, and once again O’Connell exuded a certain calmness about Ireland’s difficulties in this set-piece since the warm-up games.
“We haven’t done a lot differently really. Against South Africa, it was a tough start, they were good defensively, we were probably poor on our behalf on the drill. And they managed to sneak an extra man in for one of the lineouts close to their line which was disappointing, but fair play to them.
“What I was really delighted with was how the lads worked through it, how Rónan Kelleher and the lineout leaders worked through it, figured it out and got us back on track.
“We’re against a real good lineout side this weekend again who can cause problems for teams and I’m sure they’ll cause us a few problems as well and it will just be down to how we react and how we handle them.
IRELAND v Scotland (possible): Hugo Keenan; Mack Hansen, Garry Ringrose, Bundee Aki, James Lowe; Johnny Sexton (capt), Jamison Gibson-Park; Andrew Porter, Dan Sheehan, Tadhg Furlong; Tadhg Beirne, James Ryan/Iain Henderson; Peter O’Mahony, Josh van der Flier, Caelan Doris.
Replacements: Rob Herring/Rónan Kelleher, Dave Kilcoyne, Finlay Bealham, Iain Henderson/Joe McCarthy, Jack Conan, Conor Murray, Jack Crowley, Keith Earls.