Chris Wyatt has won 36 caps for Wales

The 22-year-old Dragons forward, who can play in the second and back rows, will be out of action for at least six weeks.

Llanelli Scarlets lock Chris Wyatt has been called up as Owen's replacement.

Wyatt, 30, was a surprise omission from Steve Hansen's original 30-man squad.

Said Wales coach Hansen: "Michael injured his back prior to going on our warm weather training camp to Lanzarote, and after seeking specialist advice, we have decided not to risk him by taking him to Australia.

"The injury means he will be out for a further six weeks or so. At 22, he is still a young man and he has a lot of rugby left to play so we have taken the common sense option and decided his long term future is more important that his short term future career.

"Michael understands the situation and we are lucky to have an able replacement in Chris Wyatt to bring into the squad.

"Chris was unlucky to miss out on the final 30-man draft and we are pleased to welcome him back on board."

Wales fly out to Australia next Monday, and play Canada in their opening Pool D match on 12 October.

Wales World Cup squad

Backs: Kevin Morgan (Celtic Warriors), Rhys Williams (Cardiff Blues), Garan Evans (Llanelli Scarlets), Gareth Thomas (Celtic Warriors), Mark Jones (Llanelli Scarlets), Mark Taylor (Llanelli Scarlets), Tom Shanklin (Cardiff Blues), Sonny Parker (Celtic Warriors), Iestyn Harris (Cardiff Blues), Stephen Jones (Llanelli Scarlets), Ceri Sweeney (Celtic Warriors), Gareth Cooper (Celtic Warriors), Dwayne Peel (Llanelli Scarlets), Shane Williams (Neath-Swansea Ospreys).