Wales winger George North will miss his club's biggest game of the season as he recovers from a third head injury in four months.
Experts have also warned North that he should not play again until the Rugby World Cup.
North, one of Europe's top rugby players, was knocked unconscious while playing for Northampton in its 52-30 win over Wasps in the English Premiership on Friday.
He was also concussed playing for Wales during the November internationals, and the recent Six Nations.
Northampton coach Jim Mallinder says North will not play in Saturday's match against French team Clermont-Auvergne in the quarter-finals of the European Champions Cup.
"It's a tough game, (but) player welfare will always come first," Mallinder said on Wednesday.
North will be assessed by a neurologist this week.
Share
