The 31-year-old endured a tormenting season last term. He featured just six times for Leinster and twice for Ireland, missing out on the entire Six Nations title campaign, a summer tour to Australia and the run-in to the province’s double-winning league and European Cup campaigns.

It is five months since he has played. Nine since he put games back to back.

A combination of hip and shoulder injuries were to blame for the inactivity. O’Brien launched two failed comebacks last term but he trained twice last week and is now expected to take a full part in contact ahead of the province’s away game with Connacht on Saturday.

The reports are that the Carlow man has been ripping it up in training and forwards coach John Fogarty hinted at the hunger shown by the Ireland international to play again while touching on the need to be absolutely certain he is ready. Nobody wants or needs another false dawn now.

“The only thing is he’s five months out and they will be watching like hawks over the week,” said Fogarty of the Leinster medical staff who must also see whether James Ryan and/or Dan Leavy can pass return-to-play protocols after suffering head injuries in the defeat of Edinburgh last weekend.

A place on the bench for the weekend’s Guinness PRO14 trip to Galway would be a good starting point for O’Brien, a two-time British and Irish Lion who must have felt pangs of envy as he looked on at Josh van der Flier in recent weeks.

The Dubliner was told to factor in a nine-month absence from the game after he ruptured a cruciate ligament in his knee during Ireland’s Six Nations game against France in Paris last February. He made it back in seven.

Van der Flier’s rehab programme, under the watchful eye of Leinster physio Fearghal Kerin, was aided in part by the knowledge that the province’s medics had already stored in treating similar issues with his teammates Jordi Murphy and Tom Daly.

And Bernard Brogan played a part, too.

The Dublin footballer, who had torn a cruciate in a training session in February, was operated on by Ray Moran in the Sports Clinic in Santry on the same morning as van der Flier — Brogan actually made his return to the field after just five-and-a-half months.

Yeah, it was incredible,” said van der Flier. “He was trying to get back for the end of a (GAA) season and it would have been silly for me to rush back with a whole season ahead. I was incredibly impressed (with Brogan) and he’s been doing very well for his club as well by all accounts.

Brogan had himself used the example of Fergus McFadden, who returned from a cruciate injury after five months in 2014, as a target in his own rehab programme but it still wasn’t quick enough to force his way into Jim Gavin’s starting line-up.

A handful of minutes at the back end of a nothing Super 8s game against Roscommon was the only action he saw all summer, but van der Flier has much more time to make an impact for Leinster in this campaign and he has already gone some way towards that.

Forceful performances in his two appearances to date, away to Scarlets and at home to Edinburgh, have served updated notice of his capabilities for club and country and given rise to the suspicion that he may have used the layoff to add some beef. Not so, it appears.

I lost a good bit of weight at the start (of the rehab). I lost a lot of muscle, just from the legs not being used and that sort of thing. I’m kind of the same weight as I was, but I’ve done a good bit more... I’ve done about seven months of gym, three or four times a week.

“So I’m probably the strongest I’ve ever been. It’s more strength than anything else. I definitely had put on a bit of weight and I’m back at around 104 kilos now, which is there or thereabouts from where I was in February.”