Rees has won nine Wales caps since his debut against in February 2010
Richie Rees is waiting for a European Rugby Cup disciplinary hearing that could suspend the Wales scrum-half for the Six Nations Championship.
The Cardiff Blues player was cited for allegedly making contact with the eye area of Dylan Hartley in their Heineken Cup defeat to Northampton Saints.
Blues colleague Xavier Rush was also red-carded in Sunday's 23-19 loss that ended Cardiff's Heineken Cup hopes.
Rees faces a punishment of between 12 and 156 weeks if found guilty.
His offence is more serious than the one committed by number eight Rush, who was punished with a one-week ban for a high tackle on Courtney Lawes in Sunday's forgettable day for the Blues.
Rees, Wales understudy for British Irish Lions star Mike Phillips, has been charged under law 10.4(m): "Contact with the eye/eye area; Acts contrary to good sportsmanship."
If found guilty of gouging, even a ban on the lower end of the scale would rule Rees out of most of Wales' Six Nations campaign which begins against England in Cardiff on 4 February.
A hearing date is yet to be set for Rees, who won the first of his nine Wales caps against England in February 2010.
Warren Gatland will hope Rees is available for the Six Nations as the Wales coach will already be without wings Shane Williams and George North for the start of the campaign while Lee Byrne and Stephen Jones both face a race against time to be fit.