A Leinster front-row and an Ulster back-row have been called into the squad in their place

Dan Sheehan sustained a concussion during Ireland's 42-12 victory over Argentina and the will undergo a 12-day return to play protocol.

The hooker and last week's skipper will definitely miss Saturday night's Fiji game and is tight up against Saturday week's South Africa game.

Sean Jansen (knee) has been ruled out of the remainder of the Nations Championship and will return to his province to continue his rehabilitation.

Gus McCarthy and David McCann have been called in to train with the squad this week.

Rob Baloucoune (cramp) and Josh van der Flier (ankle) will continue to be monitored over the coming days with the management hopeful that they will both be available.

Bundee Aki, who was a late withdrawal from the squad that defeated Argentina due to illness, is expected to resume full training on Tuesday.

"It's a shame," says Assistant Coach John Fogarty of Sheehan. "It didn't look like a huge amount on field, but he's going to follow his 12-day return protocols.

"But, look, it gives others opportunities and we'll see I think. It's 12 days and all going well, he'll be good to go."

It is also a blow for Sean Jansen give the door that was opened for him when Caelan Doris pulled out.

"Yeah, it's a shame for Sean. He's been really good at the start of the season with Connacht and came in, trained really, really well.

"He wanted to put a marker down and he has done in training and it's a shame he's gotten that injury.

"But he's a quality player, he's a good professional and there's no doubt he'll be back.

"It is disappointing. You care about the lads as much as anything. You want them to go well, but you care about them and when you lose someone, it's not nice.

"Sean wanted to play every game. It's not going to be, but that's how the game is."

The Fiji game was always going to see changes, it is likely Sheehan would have been rested in any case, it is unlucky for Jansen.

"The team will be named on Thursday. I think it's important we're all, from today, understanding what it is this squad needs to do to put out an improved performance on last week.

"So that's what we'll be focussing on, pick the best side for the fixture for now.

"But I think everyone's focussing on what are the improvements that need to be made and we'll get to team selection."

Meanwhile, Tom Ahern (neck), Ethan McIlroy (thumb) and Michael Milne (ankle) have been ruled out of the Ireland XV squad to face Fiji ‘A’ in Virgin Media Park on Friday, 20th November (Kick-off 7.45pm).

They have been replaced by Fineen Wycherley, Todd Lawlor and Jeremy Loughman.

The Ireland XV squad will assemble on Monday, 16 November in Cork ahead of the match that Friday which will be a double-header involving Ireland against Scotland in an U20 international (Kick-off 5pm).

**Ticket sales for Saturday’s game have passed the 45,500 mark and are still on sale from Ticketmaster.ie.