Flanker Jack Daly sustained an ACL injury in Munster's loss to Leinster in the final regular season round of the URC last Saturday evening at the Aviva Stadium.
The Kerry man was injured while being tackled into touch in the closing stages of the 35-25 loss. He will now be seen by a specialist.
Daly had only recently returned from a long-term layoff due to an ankle injury.
Three other Munster players picked up knocks in the defeat.
Jean Kleyn sustained a neck injury and has undergone a scan and will be managed by the medical department. It is not expected to be a long-term injury.
Andrew Conway had an aggravation of his previous knee injury and will be assessed this week to determine his availability.
Alex Kendellen was removed following his HIA and will undergo the return to play protocols under the supervision of the Munster medical department.
Craig Casey and Stephen Archer will return to training this week in better news for the province.
Captain Peter O'Mahony, Damien de Allende, and Simon Zebo are all expected to resume full training this week.
Neil Cronin, John Hodnett, Dave Kilcoyne, Tadhg Beirne, and RG Snyman all remain longer-term absentees.
It was revealed yesterday that Munster's URC quarter-final against Ulster in Belfast would take place on Friday week, June 3, with a 7.35pm kick off.