Injured Tupou expected back for World Cup

Dave Rennie is confident Wallabies steam-roller Taniela Tupou will be back from injury in time for next year's World Cup while promising a review into the causes of Rugby Australia's colossal casualty list.

Tupou suffered a ruptured Achilles tendon against Ireland on Sunday, with four other Wallabies also injured in the 13-10 loss in Dublin.

With former captain Michael Hooper the latest to be ruled out with concussion, nine players have now been sent home to recover from a horror European tour that's also included one-point defeats at the hands of France and Italy.

Despite Tupou's grim prognosis, Rennie allayed fears the prop enforcer would miss the World Cup in September.

"Recovery time (is) seven-plus months, so he's unlikely to get back in time for Super (Rugby) but will be back in time for international," the coach said on Friday.

The New Zealander vowed to conduct a review into the causes of the casualty glut, but dismissed claims Tupou's injury was the result of overwork.

"Obviously it's disappointing," Rennie said.

"With the amount of injuries we have, we'll have a good look into what's caused some of those. 

"Some are bad luck and others if it's something we're doing within our program then we need to adjust."

One positive for Rennie has been the opportunity to blood fringe players with valuable first team minutes.

"It's no doubt that we've got a bit of time into the group that's playing and they're not unfamiliar with what we're trying to do," he said.

"Injuries have created opportunities and that gives a chance to create more depth and competition for places."

Five-eighth Ben Donaldson will earn his first international start when the Wallabies take on Wales on Sunday (AEDT) in the fifth and final game of their spring tour.

"He's training really well, he's got points of difference and we want to find out what that's like under the blowtorch," Rennie said of the 23-year-old.

Also starting in his first match will be 21-year-old Langi Gleeson, while prop Sam Talakai could win his first cap off the bench.

With only 25 fit players to choose from, lock Darcy Swain and prop Matt Gibbon were the only two overlooked for the tour-ending Cardiff Test.

"We have a Murphy's Law group where we're slotting guys in on the chance that someone falls over on a Friday or on a warm-up that others are clear in their roles and they can jump in," Rennie said.

"It's no doubt that we've got a bit of time into the group that's playing and they're not unfamiliar with what we're trying to do. 

"Injuries have created opportunities and that gives a chance to create more depth and competition for places."