Fringe Wallabies' fly-half Christian Lealiifano will miss six months of rugby after suffering a serious ankle injury in the ACT Brumbies' Super 15 win over the NSW Waratahs last weekend, the club said Monday.

Lealiifano, 25, dislocated and fractured his right ankle in the final minutes of Saturday's 23-6 victory and will undergo surgery on Monday, team officials said.

Lealiifano was one of the competition's in-form players this season and was in contention for the Wallabies' No.10 spot in the absence of injured stars, Quade Cooper and James O'Connor.

Brumbies' head coach Jake White, who last week suggested Lealiifano would be a worthy recipient of a Wallabies' jersey off the back of his career-best form, said it was a terrible blow for the Brumbies and the young playmaker.

"That's it, he's gone for the season. Whatever the outcome of the surgery he won't be back for the Brumbies this year, which is a big blow for both Christian and the team," White said in a statement.

"It's not ideal, we spoke about it in the change room and it's not great but it's just another challenge that's been thrown up to the group."