Mortlock out of Bledisloe opener

Stirling Mortlock has been ruled out of Saturday night's Bledisloe Cup and Tri Nations blockbuster against New Zealand in Sydney.

The inspirational skipper has failed to recover sufficiently from a head knock which saw him leave the field early in the second half of his side's impressive victory over the world champion Springboks last weekend.

Western Force centre Ryan Cross, who came on as a replacement for Mortlock at Subiaco, is expected to start the match at outside centre in his skipper's absence, while fellow NRL convert Timana Tahu is likely to earn a bench spot.

Veteran flanker George Smith will lead the side in Mortlock's absence.

"Stirling was concussed last weekend (and) we had hoped that, with time, the symptoms would resolve themselves," coach Robbie Deans said.

"But that hasn't happened soon enough for this match, so we've made the call early."

“George took over once Stirling left the field in Perth and got the team over the finish line so we've opted to maintain continuity by leaving him in charge."