Leinster have confirmed that Johnny Sexton is "likely" to miss the remainder of the province's season due to a groin injury.
The Ireland captain sustained the injury during the Six Nations win over England on 18 March which clinched the Grand Slam success for Andy Farrell's side.
With Sexton set to retire at the culmination of this autumn's Rugby World Cup, it means the United Rugby Championship victory over Connacht on New Year's Day could potentially have been the 37-year-old's final appearance for Leinster.
The URC regular season ends on the weekend of 21-22 April, before the play-offs which will run until the 27 May decider. If Leinster were to reach the Champions Cup final, the European showpiece is slated for the Aviva Stadium on 20 May.
Sexton is due to see a specialist on Tuesday and undergo a procedure with Leinster effectively ruling him out of the rest of their United Rugby Championship and Heineken Champions Cup campaign.
"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 ahead of Saturday's Champions Cup first leg against Ulster.
Leinster also confirmed that Ireland internationals Garry Ringrose, Hugo Keenan and Caelan Doris will continue to follow graduated return to play protocols this week.
Jamie Osborne, Martin Moloney (both knee), Rónan Kelleher (shoulder), Joe McCarthy (ankle), Cormac Foley and Charlie Ngatai (both hamstring) remain unavailable.
Ulster said in a statement that they have "no new injury concerns" from Saturday's URC win over the Vodacom Bulls.
Will Addison (lower leg), Marty Moore (knee) and Iain Henderson (arm) all missed the 32-23 victory in Belfast.
