Ulster face a monumental task to knock out Champions Cup favourites Leinster on Saturday but Dan McFarland doesn't think their task is made any easier by the absence of Johnny Sexton.

The Ireland skipper has been ruled out of action with a groin injury and the club admitted this afternoon that he may have played his last Leinster game.

"Johnny Sexton will see a specialist on Tuesday and have a procedure on the groin injury picked up in Ireland's Guinness Six Nations game against England which will likely keep him sidelined for the remainder of the Leinster Rugby season," the province said of the 37-year-old, who is due to retire from the sport after the World Cup.

Ross Byrne, who is also Sexton's back-up with Ireland, will step into the out-half boots and McFarland is an admirer of the 28-year-old.

Asked if their job became any easier with the news that the Six Nations record point scorer and former world player of the year would miss out, McFarland said: "Any answer that I gave that was slightly close to 'yes’ would be demeaning to Ross Byrne and, to be fair, a number of other fellas in the squad who can play fly-half.

"We know well that Ross Byrne is quite capable of taking the rudder and winning games and winning games against us.

"In the Six Nations he was the back-up 10 for the best team in the world so he’s probably pretty good, in fact he is very good."

Ireland and Ulster lock Kieran Treadwell said he can see similarities in the two players and their game-management styles.

"He’s a similar enough player to Johnny," the 27-year-old told RTÉ Sport ahead of their last-16 clash at the Aviva Stadium on Saturday (5.30pm, live on RTÉ2 and RTÉ Player).

"Obviously, Johnny is Johnny. [Ross is] going to control the game and we know that.

"I’m going to sound like a parrot but it’s about focusing on ourselves and how we can impose ourselves on the game and not taking a massive focus on individuals because they’ve got loads of great individuals and so do we but it’s that collectiveness and imposing our game onto them."

Kieran Treadwell worked his way back into Andy Farrell's plans

Ulster scraped through to the knockout stages with one win, against Sale at home, and three losses to their name, albeit they picked up three bonus points in defeats to La Rochelle twice and Sale.

Leinster, meanwhile, coasted through their pool, taking maximum points from clashes with Racing 92 and Gloucester.

McFarland said he can’t wait for the challenge.

"Very excited ever since we knew we were going to be playing Leinster" he told reporters at the Kingspan Stadium this afternoon.

"It’s the biggest challenge in club rugby in the world in my opinion. Given that it’s an interpro game as well as a Champions Cup game, what’s not to get excited about?

"In terms of the team being ready we had a good Six Nations period.

"There was a lot going on in Irish rugby and we were very focused on what we were doing and getting on with that. We pushed areas of our game.

"We came out against the Bulls [in the 32-23 URC win at the weekend] and beat practically a team that beat Leinster in the semi-final last year.

"We made a bit of hard of hard going of it early on but came through a very physical encounter."

Ulster have lost twice to Leinster this season but the players will be able to lean on last season's fixtures, where the 1999 European champions did the double over Leo Cullen's men.

"We’re in a pretty good place going into this game," added McFarland.

"You’ve got to go in with confidence.

"Most people would say we don’t have a cat in hell’s chance.

"Looking at the bookies, we’re 100/1 to win the competition and Leinster are evens in a 16-team competition.

"Playing at home against a team that’s 100/1, I’d argue that most people would [say] the history would say that’s not the place for us to be.

"In terms of our own we know that over the last two years we’ve beaten them twice and we’ve played some good stuff in the other games in patches but simply weren’t good enough to beat them this year.

"We know we have the ability to win games against Leinster but we’re also fully aware that if we’re not playing to the peak of that ability it’s going to be tough going but we’re obviously very motivated."

Watch Leinster v Ulster in the Heineken Champions Cup on Saturday from 4.30pm on RTÉ2 and RTÉ Player, follow a live blog on RTÉ.ie/Sport and the RTÉ News app or listen to live commentary on RTÉ Radio 1