Ross Byrne looks certain to replace Joey Carbery for Saturday's return clash with Northampton as Leinster's out-half injury crisis deepens, while there was positive news for Seán O'Brien.

The province will learn the extent of Carbery’s ankle injury today, with the 21-year-old Byrne set to make just his fourth senior start in Leinster colours in the Champions Cup clash (Aviva Stadium, 7.45pm, live on RTÉ Radio 1).

Byrne slotted in seamlessly in the comprehensive win over the Saints at the weekend in an area that is severely testing the depth of the three-time European champions’ squad.

Carbery will see a specialist to assess the damage to his ankle and scrum coach John Fogarty insisted that Byrne is ready to step into the breach despite his inexperience.

“He was ready to start last weekend. He came off the bench last week and did a great job in how he controlled the game and led the team,” he said.

With Sexton sidelined and Cathal Marsh still working his way back to fitness, other options would have been shifting Noel Reid or Isa Nacewa into the number 10 jersey, but Fogarty is confident in Byrne’s ability and temperament.

Byrne is poised to replace Carbery in the return game with Northampton

“Noel has done it for us in the past, Isa has done it in the past, but Ross is there and as he showed last week, he is prepared to play on those big days.”

Fogarty also gave an update to Sexton’s situation after suffering a hamstring injury against Australia in the November Series.

Ireland head coach Joe Schmidt hinted that the out-half could benefit from an extended break, but the 31-year-old is expected to return to action over the coming weeks. The former Racing 92 player was in Santry today as he continues his road to recovery and Fogarty is expecting to see him don the blue jersey in the near future.

“As soon as he’s ready to come back and play, he will be back and we’d hope to see him stay healthy,” Fogarty told reporters.

“I’m sure Johnny’s frustrated watching us playing European rugby.”

Hartley was dismissed for a challenge on O'Brien

The province earlier confirmed that flanker Seán O’Brien did not suffer a concussion in the challenge that led to Dylan Hartley’s red card.

"Seánie is fine. He looks good for this weekend"

Fogarty revealed that the backrower is ready for selection this weekend, and highlighted one positive outcome to the unsavoury incident at Franklin’s Gardens.

“Seánie is fine. He looks good for this weekend. We’ll see how he gets through training, but he looks healthy.

“He was okay on the sideline [against Northampton], he just had neck stiffness.

“You don’t want players to come off injured...we were excited to get Jack Conan get his opportunity. He’s been going really well in the lead-up to this game.

“Silver linings a little bit.”

Full-back Rob Kearney is also awaiting results of a scan on an ankle injury.

Meanwhile, both Robbie Henshaw and Michael Bent came through the game with no issues.