Bernard Jackman believes Sean Cronin is facing his final shot at squeezing back into the Ireland fold when Ulster come to the Aviva Stadium for Saturday's Heineken Champions Cup quarter-final.

Hooker Cronin had a nightmare against Italy in February on what was his first ever Six Nations start. He was subsequently left off the squad for the defeat of France, falling behind captain Rory Best, Munster man Niall Scannell and Ulster's Rob Herring in the pecking order.

The ruthless competition means Cronin could pay a huge price for what was a collectively awful setpiece showing from Ireland in Rome but Jackman said the stage is set for the Leinster man to remind Joe Schmidt that he can do it when the pressure is on.

"This is Sean's chance," he told RTÉ 2fm's Game On.

"They will be in the knockout stages of the Pro14, but a European quarter-final at home, against a guy [Best] who is keeping you out of the Irish team... You could argue it's Scannell keeping him out but if Sean has a big game this weekend, it's a last-gasp chance to get back into that summer squad.

"He needs to perform. He needs to have a big game."

Jackman expects Leinster to come out on top in the derby arm wrestle but it may not be plain sailing.

"We can't judge Leinster and Ulster on what they were like in January," he added.

"It's very much on the day. Leinster have better players probably and more experience of these types of games - and they're at home - but I just think it's so hard to know.

"Ulster have had less guys involved with Ireland over the Six Nations, Dan [McFarland] has been able to prep for this game three or four weeks out, start to put things in place that he wanted to use against Leinster.

"Realistically for Leo [Cullen] and Stuart [Lancaster]... it's a race now to be ready, a race to get your A-game back. It's a potential banana skin for Leinster but it's very hard to see Ulster being good enough really."

Munster go to Edinburgh for what Jackman says is a serious mission. The Scots are lying in the long grass, and have the muscle and nous to upset the province. 

"Historically, in terms of performance in Europe, there's no comparison," he said.

"I think it's only Edinburgh's third time qualifying for a quarter-final but that's irrelevant given the experience they have.

"They made a decision last week to play all their returning internationals against Leinster for two reasons: one they needed the points in the Pro14, and two [head coach] Richard Cockerill knows this is an incredible opportunity. They're worked very hard to get a home quarter-final. They are going to be hard to beat.

"If Carbery is in I'd fancy Munster, but if he's out I think it will be very tight and Edinburgh might just get up."

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Connacht meanwhile travel to Sale Sharks in the last eight of the Challenge Cup. 

"It's two very attacking-focused teams so it should be a cracking match," Jackman commented.

"It could be the most attractive game of the weekend. Sale Sharks are very dangerous; they have a really good attack system. We know Connacht will want to play, the likes of Jack Carty is on top form.

"I think it will be a high-scoring match. It's a hard place to go. Sale have invested in their squad and I imagine they'll be looking for some silverware. The Challenge Cup is their best chance of getting it."