All Blacks prop Ben Franks has suffered a recurrence of the back injury that forced him out of last year's grand slam tour of the UK and Ireland.

Franks joined the growing list of Graham Henry's World Cup contenders on the sidelines when he was replaced by his brother Owen during the Crusaders' 42-30 Super Rugby victory over the Western Force in Perth.

He will undergo further medical assessment before the squad heads to South Africa on Monday but Crusaders coach Todd Blackadder sounded pessimistic about the front rower's prospects of making the trip when quizzed after the match.

"We're holding our breath on him but it's not looking good," Blackadder said.

"He felt a bit of a popping sensation there and he's had an injury there before in his lower back."

Last November Franks had to return home before the second leg of the grand slam against Scotland after injuring his back during a gym session.

He recovered during the off-season and has formed a strong propping unit with his sibling and loosehead Wyatt Crockett.

The trio have been rotated during the Crusaders 10 matches so far but Crockett and Owen Franks can now expect to log plenty of game time against the Stormers in Cape Town next Sunday and the Cheetahs at Bloemfontein the following weekend.

Meanwhile, in more encouraging personnel news for the Blackadder, No.8 Kieran Read's two weeks of rest and recuperation has expired so he will play the Stormers.

Daniel Carter is also expected to return at five-eighth after being unavailable with a hamstring strain.

"The cavalry's arriving shortly," Blackadder smiled.

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