Munster winger Keith Earls could be set for four months on the sidelines following confirmation he will require surgery on a knee injury.
Earls injured his patellar tendon during the close-season and will now be forced to sit out Ireland's November internationals against South Africa, Georgia and Australia.
Munster will also have to do without the 26-year-old in their European Rugby Champions Cup pool fixtures, which begin with a trip to Sale Sharks on October 18.
A four-month absence would leave Earls racing to be fit for the Six Nations opener against Italy on February 7.
Munster team-mate Donnacha Ryan is also set to sit out the forthcoming international fixtures, with his surgery on an injured foot scheduled for Thursday, while Peter O'Mahony returned to limited-contact training this week following shoulder problems.
Ireland also have concerns over the fitness of Cian Healy (hamstring) and Jonny Sexton (jaw).