The Brumbies are at risk of not having Matt Toomua for the rest of the Super Rugby season, with the star playmaker to miss Friday’s clash with the Bulls and only a “50-50” chance of coming back next week.

Toomua spent more than a month on the sidelines with an ankle injury, only to hurt the other one upon his return against the Lions in Johannesburg earlier this month.

Despite enjoying a bye week, the inside centre couldn’t prove his fitness for the Brumbies’ must-win game at GIO Stadium and remains in doubt for their penultimate-round battle with Western Force in Perth.

“He’s not as close as we would’ve liked,” coach Stephen Larkham said on Thursday.

“If he was close, we certainly would’ve pushed him out there because we know our season is sort of on the line at the moment.

“The flight (back from South Africa) probably hurt him a little bit.

“He did all his rehab last week, but just wasn’t good enough this week.

“We’re hoping for next week, but at this stage it’s still a 50-50 proposition.”

Robbie Coleman returns to the starting line-up after doing a fantastic job at No.12 in his senior’s absence, according to Larkham.

But the coach admitted Toomua was still a “massive loss”.

“We know we’ve got good coverage there, but it’ll be nice to have one of the world’s best players out on the field,” he said.

Scott Sio, meanwhile, returns after two months recovering from a knee injury.

The Samoan-born giant hasn’t played since round nine when he strained his medial ligament against the Blues, except for a 60-minute club rugby appearance last week.

Captain Stephen Moore said it was a huge boost to have Sio back.

“We’ve really missed him over the time he’s been injured,” Moore said.

“The guys who’ve filled in have done a great job, but Scotty’s a quality player and he’ll add a lot to our team when he comes back.”

The Brumbies need to beat the Bulls if they are any chance of reclaiming top spot on the Australian conference.

They sit three points behind the NSW Waratahs on the local ladder, but are narrowly holding down a wildcard spot for the finals in sixth overall.

The Bulls are also three points adrift of South African conference leaders the Stormers and are in desperate need of a victory.

“We’re both in very similar positions, so we need to be more desperate tomorrow to win,” said Moore.