Wales' Dan Biggar is assisted after he was injured against Fiji. Photo: Aaron Favila/AP Photo

OITA – Wales coach Warren Gatland said they would have to run players out of their usual positions after a bruising 29-17 win over Fiji booked a place in the World Cup quarter-finals but left flyhalf Dan Biggar groggy with a second head injury.

Biggar has been ruled out of the last pool game against Uruguay on Sunday after being forced from the field in the second half at Oita Stadium following a sickening collision with team mate Liam Williams.

There are further concerns over hat-trick hero Josh Adams and centre Jonathan Davies, with both suffering leg injuries.

"He (Biggar) didn't do an HIA (head injury assessment), it was just because of the contact (that) he was just removed from the field," Gatland said of Biggar's injury at the post-match media conference.

"Which means he’s not in consideration for Sunday and he’ll have to go through the protocols and we’ll probably have to get someone in to have a look at him as well."

It was Biggar's second head knock at the tournament after he was taken from the field following a collision with Australia centre Samu Kerevi during the previous pool win in Tokyo.

Rhys Patchell has backed up Biggar at flyhalf but Gatland was unsure who he would have in reserve if Patchell went down.

"I don't know, we'll probably sit down as coaches and look at that," he said.

"Some players are going to have to back up (against Uruguay), we may have a 6-2 (forwards-backs) split.

"We've got players who will be a little unfamiliar but we have been running players at training in those positions.

"With the short turnaround we need to freshen some players up and hopefully we're good enough to do the job on Sunday to secure this group."

Gatland played down concerns over Adams and Davies as "dead legs" but said linchpin centre Davies would be taken for a scan, having been struck on the knee in a collision.

The costly bonus point win put Wales top of Pool D ahead of second-placed Australia.

Victory over emerging nation Uruguay would ensure Wales stay top and enjoy a potentially kinder route through the quarter-finals against the runner-up of Pool C.

Pool C rivals England and France are scheduled to play off for top spot in Yokohama on Saturday but the match has been thrown in doubt by the approaching Typhoon Hagibis.

Although Wales will be forced into player management contingencies ahead of the knockouts, Gatland was thrilled with his team's ability to rally twice from behind in a see-sawing and highly entertaining contest against the Fijians.

"It was tough but there was some real character displayed," he said. "We're absolutely delighted (to be in the quarter-finals). I think everyone’s fear is to try to get out of your pool." 

Reuters