Wallabies hit by Gerrard injury

Australian utility back Mark Gerrard is out of the World Cup after injuring his knee in the Wallabies' 91-3 romp over Japan on Saturday.

Scans taken after the match confirmed that Gerrard had ruptured the medial ligaments in his left knee and would take no further part in the tournament.

The 25-year-old fullback or wing will return to Australia later this week with coach John Connolly expected to name a replacement within the next few days.

"It's disappointing, especially at this point of the tournament," Gerrard told reporters.

"I pretty much knew straight away, when I heard it click, what would happen after that."

Gerrard has been plagued by knee problems in recent seasons and was on the field for less than a minute against Japan when the injury reoccurred.

Coming on as a late replacement with the game already wrapped up, Gerrard fielded the ball from the kickoff and instinctively charged straight at the defence only to twist his knee in the tackle.

He was told by doctors that he would not require surgery but would have to wear a leg brace for the next six to eight weeks before beginning rehabilitation.

Cameron Shepherd, who has played five tests for Australia, is looming as the most likely replacement although Connolly said he was also considering Clinton Schifcofske, Lachlan Turner and Digby Ioane.

"We've got people on our shortlist back home and we'll probably check their form first," Connolly said.