Australia backrower David Pocock has been ruled out of the Rugby World Cup clash against Ireland because of a back injury, giving Ben McCalman his first test start on the openside flank.

The loss of Pocock, one of the premier ball fetchers in the game, is a serious setback for the Wallabies ahead of the key Pool C match with Ireland.

The losing team is likely to ultimately join the side of the knockout draw which contains the defending champion Springboks and top ranked All Blacks.

Pocock missed Australia's last training session on Friday after waking up with soreness in his lower back, a complaint that has troubled him before.

Wallabies will take on Ireland at 8.30pm.

Story by: Dreu Vukailagi