Ireland internationals Jamie Heaslip and Rob Kearney have been ruled out for a "number of weeks", casting doubt on their availability for British and Irish Lions selection.
Neither player featured in Ireland's Six Nations victory over England last weekend, with Heaslip pulling out during the warm-up due to a back injury.
Kearney, meanwhile, sustained a knee problem in the week ahead of that match and Leinster coach Leo Cullen is reluctant to set a concrete return date for either player.
"It's hard to be definitive with timelines," Cullen said of Heaslip, with the Lions' first Test against New Zealand scheduled for June 24.
"Jamie just had a procedure done on his back this morning. He had disc issues. Obviously they come on quite quickly.
"He trained the week of the England game, pulled out in the warm-up - at the very end I believe. He had a bit of discomfort at the start of the week, so he saw a specialist.
"He saw somebody again yesterday afternoon, so he was straight in and had a procedure done this morning.
"It obviously rules him out of the next number of weeks. When we get a report we'll find out how long that will be. It sounds like they're reasonably standard procedures."
Explaining the Kearney situation, Cullen added: "Rob had an issue with his knee. It happened early in the week in training the week of the England game.
"He had a procedure done during the week after seeing a specialist on Tuesday. That's probably four to six weeks. We'll see how he comes through that."