Former Wallabies hooker Brendan Cannon predicts the Western Force will struggle to recruit and retain top-line players if James O'Connor defects to Super Rugby newcomers Melbourne Rebels.

Rumours are rife O'Connor is set to sign with the Rebels, who earlier this week poached star Wallabies and NSW Waratahs fullback Kurtley Beale for the next two seasons.

Despite the speculation, the Force remain optimistic they will retain the 20-year-old.

But Cannon, an inaugural player who still has close ties to the club, said the Perth-based franchise would struggle for years to come if O'Connor did jump ship.

"He's someone that they've fostered and harnessed out of school, he's someone they were looking to build future sides around," Cannon said on Friday.

"He's a superstar ... every game he's played at flyhalf or fullback for the Force he's been one of their best players."

The Force have worked hard to keep the core of their playing list, re-signing Wallabies flanker Ben McCalman for a further two years on Friday to add to the signatures of skipper Nathan Sharpe, Nick Cummins and Sam Wykes.

Coach Richard Graham hesitated for several seconds when asked whether the franchise was confident of retaining O'Connor, before eventually replying: "Mate I am confident that we can retain James.

"We've presented a good program to him for the last four years and he's an important part of our squad at the moment. I'd like to think he'd stay with us."

Cannon said the Rebels' solid form, plus the potential to secure big third-party deals, made them attractive.

"I think probably what has accelerated the signing of Kurtley Beale and possibly James O'Connor is how the Rebels have gone this year," Cannon told Fox Sports.

"I think they've surprised a lot of us.

"They've won three (games), their season to date has been exceptional compared to how the Western Force were in their inaugural year.

"So from a rugby players perspective, you look at it and think ... it's a good group, you can see there's a really happy culture there, (coach) Rod Macqueen has done an exceptional job with a pretty diverse playing group and they've got some success along the way."

The Force will be desperate to notch just their second win of the season when they take on fellow strugglers ACT Brumbies in Canberra on Sunday.

O'Connor, who has shaken off the effects of a virus, will move from fullback to inside centre, but utility back Cameron Shepherd was ruled out after experiencing headaches following last week's heavy fall on his head and neck.

FORCE (15-1): Pat Dellit, Nick Cummins, Rory Sidey, James O'Connor, David Smith, Willie Ripia, Brett Sheehan, Ben McCalman, Jono Jenkins, Richard Brown, Nathan Sharpe (capt), Sam Wykes,Tim Fairbrother, Ben Whittaker, Kieran Longbottom. Res: Nathan Charles, Pek Cowan, Tom Hockings, Tevita Metuisela, James Stannard, Gene Fairbanks, Alfie Mafi.

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