Cardiff Blues fly-half Rhys Patchell is suffering from severe memory loss after being knocked out in last week's game against Ulster.
The Welsh international spent the night in hospital after the game where he was knocked unconscious by Ulster number eight Nick Williams' forearm smash.
Williams was handed an eight-week ban for the offence, but it seems Patchell will need a while to recover and he has already been ruled out of the Challenge Cup quarter-final with the Dragons.
According to WalesOnline, Patchell has no memory of the entire trip to Belfast, stretching from Thursday's flight all the way to his return to Wales.
It is unclear how long he will be out of action, with concussion very much in the limelight in rugby at the moment.
"Rhys will undergo the game’s return to play protocols but we are unclear when he will be fit to resume," said Blues chief executive Richard Holland.
“With concussion there’s no definitive time-scale for a full recovery. It could be days, weeks, months or worse."