Quade Cooper suffered a knee injury as the Wallabies ended their ill-fated World Cup with a fighting 21-18 victory over Wales to take third place.

The erratic flyhalf, who has been under intense scrutiny and regularly booed while playing in his native New Zealand, collapsed to the ground in agony while running the ball inside the Welsh quarter in the 22nd minute.

Cooper, who had played every minute of Australia's previous six games at the tournament, clutched his right knee and replays showed he'd suffered a hyper-extension while changing direction.

The Wallaby flyhalf was led from the ground, his tournament over, but this time to a backdrop of respectful applause from the crowd.

Cooper later went up to the presentation dais with his teammates on crutches to receive a bronze medal in a poignant ending to his eventful tournament.

Australia coach Robbie Deans said in the absence of a full medical diagnosis, he suspected Cooper had ruptured his anterior cruciate ligament in his right knee, an injury which can require up to nine months' rehabilitation.

"Having experienced it myself and witnessed the event I suspect it's a ruptured ACL (anterior cruciate ligament)," former All Blacks fullback Deans said.

"Quade is aware that it's a significant injury but with technology these days he'll come back good to go, you actually end up with a stronger ACL post-operation these days than prior, so he'll be back in Super Rugby (early next year).

"That whole experience, that adversity will challenge him, but I've got no doubt he'll come out of that stronger for it."

The Australians, digging deep in defence and a man-of-the-match performance from Berrick Barnes, who filled in for Cooper at flyhalf, suffered a high attrition rate in their final outing at the tournament.

Fullback Kurtley Beale re-aggravated a hamstring injury which had kept him out of last weekend's 20-6 semifinal loss to the All Blacks and lasted just nine minutes against Wales.

"Kurtley had a recurrence of his hamstring strain, so strain on strain is not ideal, but I don't think it was excessively bad, I don't think he tore it (hamstring) but obviously it didn't cope well in the game," Deans said.

Meanwhile Nathan Sharpe's 100th Test was curtailed after 46 minutes, the veteran lock having soldiered on gamely with knee trouble suffered in a heavy line-out fall early on.

Scrumhalf Will Genia and hooker Tatafu Polota-Nau were other Wallaby casualties, while captain James Horwill was replaced in the final 10 minutes.

"It was pretty torrid with a high attrition rate and the boys showed their momentum by the way stuck at their task," Deans said.

Horwill said team pride and a determination to give Sharpe a winning 100th Test match were behind the victory.

"It means a lot to us to pull on that jersey and to play not only for each other, but we wanted to make Sharpie's night a memorable one for the right reasons and so that was a big factor as well," Horwill said.

Deans said he expected some fans would be frustrated by the Wallabies' troubled World Cup campaign, which saw them suffer a shock pool defeat by Ireland before being well-beaten 20-6 last weekend by an All Blacks side they'd defeated to take the Tri-Nations title.

"There will be elements who will be frustrated as we are, that we didn't achieve more, our sentiments are identical," Deans said.

"Internally, I'm proud with the way these blokes stuck to the task, particularly this week.

"They showed not only what it meant to them, but also there's a lot of valuable substance in this group that you will see more of over the next few years."

AFP