Hickie's hopes were dashed against Australia
Ireland's Denis Hickie is flying home from the World Cup after picking up an Achilles injury in the defeat to Australia.
The winger, who has scored 23 tries for Ireland in 44 appearances, ruptured his right tendon shortly before half-time.
Ulster wing Tyrone Howe will replace Hickie as Ireland prepare for their quarter-final against France next Sunday.
"It's serious and requires immediate surgery," said coach Eddie O'Sullivan. "He could be out for up to six months. It's worse than a broken leg.
"It's a big blow because of Denis' sheer speed but Tyrone Howe is in brilliant form for Ulster at present and he won't let us down if we need him.
"Denis will be replaced by Howe from Ulster who is currently in a hotel in Dublin waiting to get kitted out, get on a plane and be here asap."
Howe won the selectors' attention on Friday with a superb display against Cardiff, in which he ran in a stunning solo effort from his own try line.