Leinster have confirmed that flanker Dan Leavy will miss this year's World Cup with a significant knee ligament injury.

The 24-year-old came on as second-half replacement in Leinster's 21-18 Champions Cup victory over Ulster at the weekend but lasted just 11 minutes after he went down with a serious knee injury.

Leinster confirmed on Saturday that Leavy's season was over, but a scan yesterday revealed that the injury is more complicated that was initially thought.

A statement from the province revealed that he must have further assessment, but that he will not be fit in time for the Autumn's World Cup.

The statement read: "Leinster Rugby can confirm that Dan Leavy had an initial scan yesterday on a complex knee ligament injury but needs further assessment this week.

"He has been ruled out for the remainder of the season and into next season to include the Rugby World Cup.

"We know the Leinster Rugby family and all of @OLSCRugby will join us in wishing @DanLeafy94 the best of luck with his recovery over the coming weeks and months."

Leavy was superb throughout last year's Six Nations as Ireland completed the Grand Slam, but has struggled with injury in the wake of the subsequent summer tour to Australia.

The 24-year-old openside had just recovered from the long-term calf injury that forced him to miss the recent Six Nations campaign.

"Dan worked so hard to get himself back and physically fit," Leinster scrum coach John Fogarty said.

"He's such a huge threat on either side of the ball, gives the team a lot confidence so it's a big loss for Leinster and Irish rugby. He'll make a plan now to get himself back."