O'Brien looking unlikely as Ringrose and Tracy ruled out
Sean O'Brien has emerged as an unlikely candidate to combat Glasgow Warriors in pool three of the Champions Cup at the RDS on Sunday (KO 1.0, Sky Sports Action).
The Ireland flanker has been bothered by a hip injury picked up against Exeter in the first leg of their back-to-back matches before Christmas.
O'Brien played through the pain barrier for 57 minutes against the English champions at the Aviva Stadium one week later.
The Tullow Tank has not been seen since, missing out on all three of Leinster's recent inter-provincial derbies.
"Perhaps when we look back in hindsight on the Exeter games, when we went back-to-back, we picked a relatively similar team," reviewed senior coach Stuart Lancaster.
"Perhaps, that's why we started slowly. Who knows? That's the strength of Leinster rugby at the moment."
Since then, the Man-of-the-Match impact of flankers Dan Leavy, against Munster, and Josh van der Flier, against Connacht, might have convinced Lancaster that they won't risk O'Brien again.
In addition, Leavy has recovered from a back problem suffered against Connacht to train fully yesterday.
Already, Garry Ringrose has been ruled out for approximately six weeks with syndesmosis from the Ulster match.
This will hurt Ireland coach Joe Schmidt as much as Leo Cullen, given the Six Nations re-appears in less than four weeks.
"Garry is actually very philosophical about it," said Lancaster.
"It's not something that he could have controlled.
"He would have been frustrated with himself if it had been a soft tissue injury, where he hadn't done his prep or warm-up work as well as he could have done.
"It's just one of those things that happens in a contact sport like rugby."
The loss of hooker James Tracy to a dislocated elbow for around five weeks has been balanced out by the return of veteran Richardt Strauss from a blow to the lower back.
At a time when Leinster are bulging with wing options, Adam Byrne has been hampered by a niggling knee injury.
It has flared up again and the Naas man has been scheduled to see a specialist later this week.
It isn't all bad news, as tight-head Tadhg Furlong is on course to make it back from his return-to-play protocols against Glasgow.
Centre Rory O'Loughlin has also completed his protocols to launch his bid for inclusion on Sunday.
Joey Carbery will also be back in the conversation for a role, either from full-back or from the bench, on his return from a small fracture to his arm.
"His first training session was the end of last week," said Lancaster.
"He certainly looked fit and well on Thursday.
"He'll be available for selection for a highly contestable position there at 15 or 12."
There is an outside chance second row James Ryan's ankle will heal in time.
Leinster might not be inclined to push the boundaries given how the 21-year-old has picked up a number of minor injuries this season.
At worst, there is comfort for Schmidt in knowing his third lock is not far away from a hit-out ahead of the Six Nations.