Ulster pair Craig Gilroy and Declan Fitzpatrick have until Thursday to prove that they are fit to face Leicester Tigers at Welford Road in Saturday's crucial Heineken Cup Pool 5 date with Leicester.
Both suffered concussion in Ulster's 27-16 victory over Montpellier on Friday night – and, under the IRFU's strict new rules designed to ensure players are not rushed back too quickly following a head injury, they must be monitored closely and tested for six days.
Only after that procedure will a decision as to whether or not it is safe for them to resume be taken.
Those in the 14,000 Ravenhill crowd on Friday night saw a clearly dazed Gilroy being led from the pitch after sustaining a broken nose.
He was scheduled to see a specialist last night, after which he will be required to follow the IRFU's normal return-to-play protocols.
Fitzpatrick (right) was concussed, having entered the fray as a 60th minute replacement for 2011 New Zealand World Cup winner John Afoa. At the time, no-one was aware of his injury; indeed, it only came to light yesterday.
Like Gilroy, Fitzpatrick – who last week signed a three-year IRFU/Ulster contract extension – is being managed as per the requirements of the return-to-play programme.The rules governing professional rugby players and amateur, club-level participants are different.
With full-timers being super-fit as well as closely watched by medical staff, they can return to action within six days of suffering a concussion provided they pass a series of tests. If there is any doubt, the protocol is that they are withdrawn. Ulster supporters have been somewhat confused by this two-different-rules-for-the-same-problem format, the widespread belief being that a concussed player must be rested for three weeks.
That is because in a new initiative launched in December highlighting the danger of head injuries, the IRFU stated that for a player who has suffered concussion, the minimum time out is 21 days, following which he can only resume having adhered to the IRFU's graduated return to play format.
Dr Rod McLaughlin, the IRFU's Head of Medical Services said: "Rugby, like all contact sports, can result in injury. Potentially serious injury such as concussion must be taken seriously from the outset."