Kearney and Heaslip hoping for May return
The multiple European title-winners underwent respective lower back and knee procedures last week and, if they are to return, it may not be until the final days of May - just when Leinster hope to be in the final stages of their twin title assaults.
"I'd be optimistic about that but I couldn't say anything more than that," said coach Stuart Lancaster, whose caution suggests that a possible Champions Cup final - May 13 - may prove beyond the injured duo's grasp.
"The Pro12 final is the last game of the season, if we get that far, and that will be the last week in May so there is still a fair bit of the season to play out.
"Both players will certainly be targeting that."
It also confirms that neither man will get another opportunity to impress Warren Gatland before he names his Lions squad next month; Kearney is slated to be out for a vague "four to six weeks".
Heaslip is clearly more imperilled as his return to play cannot even be determined yet.
That will only happen after he is "assessed further over the coming weeks" according to Leinster.
In the short-term, Heaslip's likely replacement, Jack Conan, hopes to get on the paddock tomorrow after a tight calf precluded him from playing against Cardiff; that and the likelihood he would be required this week.
Dave Kearney returns to training tomorrow but Lancaster has passed him fit. Johnny Sexton has rested up well.
Sean Cronin (hamstring), Rory O'Loughlin (shoulder), Josh van der Flier (shoulder), Zane Kircher (hamstring) and Isa Nacewa (knee) are all expected to be fit.
Asked how Leinster could compensate for the absence of two key leadership figures, Kearney and Heaslip, Lancaster shrugged.
"Take Jack Conan," he smiled. "I think it's a pretty handy replacement."
As per competition rules which allow for additional players prior to the knock-out stages, Leinster have called up prop Ed Byrne, completing his remarkable return from injury, as well as wing Barry Daly and centre Tom Daly.