The 24-year-old only made his debut for Ireland in their first warm-up game against Scotland, but his impressive performances looked to have cemented his place on the plane to New Zealand.
However he was forced off in the second half of the 26-22 defeat to Les Bleus in Dublin, and it has been revealed he suffered ligament damage which will keep him out of action for approximately six weeks.
That puts him out of contention for the World Cup with a scheduled return to fitness for Munster's RaboDirect PRO 12 game at home to Aironi.
And Ireland manager Paul McNaughton admitted it was a big blow for the promising youngster.
"The squad and management are bitterly disappointed for Felix to suffer an injury at such a vital time in terms of selection for the final touring party," he said.
"He had certainly put himself into contention over pre-season and the games in the last three weeks.
"We all wish him a speedy recovery and that he is back playing as soon as possible."
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