Simon Easterby insists Sean Cronin was left out of the Ireland squad in an attempt to broaden the playing pool ahead of this year's World Cup rather than a reaction to his performance against Italy.

The Leinster hooker made his first Six Nations start in the scrappy win in Rome but has been omitted entirely from the 37-man training group ahead of Sunday's clash with France.

Captain Rory Best, Munster man Niall Scannell and Ulster's Rob Herring are the hookers selected by Joe Schmidt.

"We're just looking to continually build some depth and find out a bit more about players that we need to work with towards what's coming up in the next couple of weeks and the end of the year," Easterby told RTÉ Sport.

"Sean has been involved in the first three games, he has started in Italy, and in a specialist position like hooker, (it's) probably only nine and maybe 10 as well where you don't get guys playing other positions.

"We know a lot about Sean. He has been in camp a long time, he has been in the squad a long time and has a lot of caps. It's an opportunity to see a bit more of other players. 

"That doesn't exclude him from next week and it certainly doesn't exclude him from us going forward. We need to keep building that depth and knowledge of those players in that position."

Ireland lost five lineouts against Italy but Easterby said it would be simplistic to lay the blame at Cronin's door.

"I think Sean has gone pretty well. There would be a couple of lineouts that have gone astray but some of them is strategy. In a lineout, there are so many combinations. If you get one of those things wrong, the lift, the jump, the throw, the movement, well it's probably the hooker that gets a little bit of the pressure.

"I can hold my hand up in terms of strategy in that Italy game. The opposition read a couple and that sometimes is the case."

Cian Healy (L) and Sean Cronin

Prop Cian Healy sympathised with his Leinster team-mate and said it just underlined the intensity of the battle for places.

"It's a tough one," he said. "That's the competition of the squad.

"It speaks volumes of the players that are here to know that Nugget can be left back with Leinster training and someone else can step in of the same quality.

"When you know people are so close to you and everyone's vying for that shirt, everyone has to keep it up. 

"That's international rugby, you have to be at your peak or someone's going to take it."

Ireland captain Rory Best

Easterby added that the likes of Herring and Scannell were being blooded with a view to making an impact off the bench during the World Cup rather than challenging for Best's starting spot.

"We're not looking past the French game in that sense but I think these games do give us an opportunity to look at depth," said Easterby.

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"We are continually looking for the best fit, the best combos. I think Bestie is playing well. He's a fit man for his age. I'm not saying 35 is an age where you go downhill. He's going really well. But we have to be really careful in that position where we are potentially travelling to a World Cup.

"You need to know a little bit more about other players and if you lose a player of Bestie's quality you have to know more about the players we need to bring in."

Follow Ireland v France on Sunday (kick-off 3pm) via the live blog on RTÉ.ie/Sport and the News Now App, or listen live on RTÉ 2fm, with commentary from Michael Corcoran and Donal Lenihan.