The Waratahs are sweating over a number of key players as they head into their final warm-up game against the Crusaders on Thursday.  

NSW centre Rob Horne will be sidelined for at least one month with a hamstring tear as new coach Michael Cheika deals with a spate of backline injuries just over a week out from the Waratahs' Super Rugby season opener.

Cheika confirmed on Tuesday the injury-prone No.13 Horne has a grade two hamstring tear and will miss four to six weeks.

Also on the injured list is winger Drew Mitchell (calf strain), who is expected to miss Thursday's trial against the Crusaders in Sydney.

Five-eighth options Berrick Barnes (knee) and Bernard Foley (ankle) are rated 50-50 chances of starting in the Waratahs' opener against the Reds in Brisbane on February 23.

Also in doubt for the start of the season is exciting winger Peter Betham who is battling an ankle injury.

The setbacks to playmakers Barnes and Foley has given 22-year-old Super Rugby rookie Ben Volavola a huge chance to stake a claim for the No.10 spot when he goes up against Crusaders and All Blacks superstar Dan Carter on Thursday.

"They're [injuries] a bit troubling because they are all around that same position that 10, 12, 13," Cheika told AAP.

"But sometimes the circumstances push something to the surface and Ben Volavola is going to get a good chance to take the lead in the race for that 10 jersey.

"There's a few options at 12 obviously. Tom Carter, Michael Hodge are options.

"It just depends on the mix. At this stage I'm not too worried about next week [Reds]. We'll just see who plays well in Thursday's game and try and pick a team from there."

Former Randwick No.8 Cheika has backed Volavola to rise to the challenge of facing Carter after a couple of impressive showings in trials.

"He'll probably be so excited about going out to match up against a guy like Dan Carter," he said.

"And it's up to the rest of the of the team to make sure he can challenge one of the best players in the world in his own position."

Cheika will also throw a rugby lifeline to 30-year-old former Western Force and Melbourne Rebels pivot James Hilgendorf who has returned to Sydney and is working as a teacher.

"If he's feeling comfortable with everything he can have a run on Thursday," he said.

"It would be a big ask for him because he hasn't done a lot of training but that's alright.

"Obviously we've got Sam Lane's contract that we can refill. If James puts his hand up then he's a chance of taking that contract in a few weeks."