The British and Irish Lions tour has taken a heavy toll on Leinster, with Hugo Keenan set to be out until early 2026, while Joe McCarthy may not return until November.
Keenan will be sidelined until the new year after having surgery on a pre-existing hip injury, while McCarthy is still struggling with the foot issue that saw him miss the second and third Lions Tests in Melbourne and Sydney.
The rest of Leinster's Lions contingent returned to training last week, although Thomas Clarkson and Jamie Osborne are the only two who are likely to be involved in the province’s opening two URC games in South Africa against the Stormers and Bulls.
"Joe [McCarthy] picked up an injury during the tour. He’s aggravated it a little bit, that’s an issue with his foot," Cullen told RTÉ Sport at an open training session at Greystones RFC.
"He’ll feature at some point, I’m not exactly sure when, but he won't probably feature for Leinster in that first block of games leading into November. Let’s see exactly when he does return.
"Hugo [Keenan], on the flip side, he had surgery post Lions tour, and that’s with a hip issue that had been bothering him prior to that. He’s making steady progress but probably won't feature until the new year.
"Two players, very experienced in recent times for us and we’ll help them and get them right. From what you would have seen here today, a lot of the Lions crew who were there in Australia have integrated pretty seamlessly into the group.
"A lot of them won't travel to South Africa but we’ll get them up and running pre-November."
Leinster and Ireland captain Caelan Doris appears to have an outside chance of being available for Ireland’s Autumn Nations Series Tests.
The captain missed the summer Lions tour due to a shoulder injury picked up in their Champions Cup semi-final defeat to Northampton Saints in May.
"He’ll be in and around November," Cullen added.
"He’s making good progress from the shoulder surgery towards the tail end of last season. He’s worked hard, but again, around November."
Garry Ringrose and James Ryan are both expected to be available to return to action along with the main core of Leinster’s Lions, who will be filtered back into the team for rounds three and four of the URC.
Ryan was carted from the pitch with a worrying head injury during the third Lions Test in Sydney, while Ringrose missed all three Tests with concussion, and took himself out of consideration for selection for those second and third Test after self-reporting his symptoms.
Both players were back on the training pitch at Dr Hickey Park in Greystones today, and Cullen says they have taken every precaution with their return to play.
"They would have gone through the process and seen the Independent Concussion Consultants (ICC).
"We’ll try to take as good care as possible. What Garry [Ringrose] did is pretty remarkable, obviously, during the summer.
"The James [Ryan] one, James has had a history [with concussion]. He hasn’t had an incident like that in over two years, I think. But it's technique. Technique is what we will continue to push.
"And obviously, when players do get bangs, they’re going to be looked after as well. So, there’s a stronger process.
"You can see the games, the games are physical. A lot of guys would be playing on in the past, whereas, obviously, everyone's seen that they’re not playing on now," he added.
