SEAN O’BRIEN WAS ruled out of selection for Saturday’s Guinness Pro14 derby clash with Munster because of a calf problem, but the strength in Leinster’s back row resources means his enforced absence barely constitutes as a blow.

O’Brien ‘got a stamp on his calf’ during his first appearance of the season last week in the win over Edinburgh and wasn’t considered for tomorrow’s showdown at the Aviva Stadium [KO 2pm, Sky Sports and TG4].

Jack Conan comes in as a direct replacement for O’Brien at the back of the Leinster scrum while Jordi Murphy drops out for Josh van der Flier in two of six changes in personnel Leo Cullen has made for the interpro.

Despite O’Brien’s unavailability, the Leinster head coach is happy with the balance of his back row unit, one which some quarters would perceive to be the province’s strongest as Rhys Ruddock continues at six.

“When Sean went to run this week he just wasn’t happy,” Cullen explained. “There’s good balance in the back-rowers we have starting and there’s some good match-ups there.

“Rhys and Peter O’Mahony, Josh against Tommy O’Donnell and Jack against CJ Stander. Even Jordi and Jack O’Donoghue on the bench as well. Both teams are very well stocked in that area.”

While O’Brien drops out of the matchday squad, another one of Leinster’s 2017 Lions is set to make his seasonal re-appearance with Robbie Henshaw named in midfield alongside Rory O’Loughlin.

With Fergus McFadden and Dave Kearney both falling out of contention this week, Cullen has opted for Adam Byrne and UCD’s Barry Daly on the wings, which will surely inject a bit of pace into Leinster’s attack.

Johnny Sexton continues as captain and partners Luke McGrath in the half-backs again, with no surprise the outstanding Joey Carbery is retained at fullback.

Leo Cullen and Jack Conan. Bryan Keane / INPHO Bryan Keane / INPHO / INPHO

Cullen admits there were a lot of difficult calls to make this week.

“Everyone wants to play in this game so we had some tough choices and tough conversations with guys as well because they all want to play. We used a lot of players over the course of pre-season so it gets to the point where it gets very congested.

“It’s a very competitive group, they’ve worked on and it’s difficult for us as coaches. It’s a tough part of the job and you’d like to pick more than the 23 in the squad but we can’t. There’s some disappointed player this week.”

Munster’s backline selection, however, comes with an element of surprise as Rassie Erasmus deploys three playmakers in JJ Hanrahan, Tyler Bleyendaal and Ian Keatley in a XV which also includes former Leinster man Andrew Conway.

When asked for his assessment of Munster’s selection, Cullen added: “I’ve just seen their team as well. Keith Earls coming back in, thought he was devastating on the tour. I watched Ian Keatley thought he played well last week. Tyler Bleyendaal has played a lot of rugby at 12. Chris Farrell is big and strong and physical with Jaco Taute obviously being injured there as well.

“Conway has played all the games so far this season and is someone that we know well. JJ at 15, he’s just a really good versatile footballer from scouting him a bit last year during his time at Northampton. They’re all very good footballers. Some good match ups there again.”

With 45,000 tickets already sold for tomorrow afternoon’s round six clash, Cullen admitted there is an extra pressure on his side to go out and perform, but all of it which is a positive.

“It’s a huge fixture for us,” he said. “For us as club it is a big fixture and we’ve a fantastic support turning out tomorrow which is great to see. To have that level of support coming out to back the team is an amazing achievement really. Everyone here has been pushing the game and it’s important we’re delivering for that level of support.”

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Henshaw returns and Sexton to captain Leinster as Cullen names team for Munster

Bleyendaal at midfield in one of four Munster changes for Leinster clash