Ireland number 8 Jamie Heaslip expects to be available for selection in four weeks after suffering a back injury against France, the IRFU has announced.
Scans on the Leinster forward revealed fractures of the transverse process of three vertebrae.
The 31-year-old number eight was forced out of Ireland's 18-11 victory over France on Saturday after receiving a knee to the back from Pascal Pape, who has since been cited for the challenge.
Although this injury causes a good deal of discomfort it does not impact on the structural integrity of the spine, and once healed should pose no long-term issues, a statement from the union's medical team read.
Heaslip is reported to be feeling “more comfortable” and hopes to be available for selection in approximately four weeks.
The 70-cap loose forward binds together the industry and grit of Peter O'Mahony and Sean O'Brien in Ireland's first-choice back row, and his absence is a clear loss to boss Joe Schmidt's side.
Ireland host England in Dublin on 1 March in a match already billed as the Six Nations title decider, with the two teams the last remaining unbeaten sides.
Heaslip's injury opens the door for Leinster back-rower Jordi Murphy to step up for that all-important England clash.
Ireland can equal their best-ever run of 10 wins on the spin against England, who were the last team to beat Kiwi coach Schmidt's side, 13-10 at Twickenham in last year's Six Nations.
France lock Pape only received a yellow card from referee Wayne Barnes for his knee to Heaslip, but was cited on Monday and will appear before a disciplinary committee this week.
The four-week timeline would rule the former Ireland captain out of the England game and possibly the Wales game on 14 March.
Meanwhile, James Cronin had a minor knee procedure last week following an injury sustained in the Ireland v Italy game. He is recovering well and will be rehabilitated in Munster.
