The winger went down late in Friday night's 32-27 loss to the Hurricanes in Wellington, the injury a devastating blow to the team.

O'Donnell was approaching the defensive line when his knee gave way and he collapsed to the ground.

The 27-year-old has impressed in his rookie Super Rugby season, scoring a hat-trick in the Brumbies recent win over the Fijian Drua but he now faces a lengthy rehab process. O'Donnell will have scans to confirm the diagnosis but medical staff currently fear the worst.

"It doesn't look good at this stage," ACT coach Stephen Larkham said. "He's pretty sad, he's had a really good year and built himself up. He's had an ACL before, everything was progressing in the right direction, now he has to go through that process again.

"We'll support him the whole way through, we know it will be a difficult process."

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O'Donnell has only been with the Brumbies for one season but he has made an immediate impact on the squad.

The Clovelly junior took a circuitous route to a Super Rugby debut. From club rugby in Randwick to a stint in Spain before three years with the Australian sevens side, O'Donnell eventually made his way to Ireland and impressed Larkham while playing for Connacht.

The injury is a major blow in the Brumbies push for the finals and teammate Nick Frost said it was tough to watch.

"When we checked on him after the game, he was blaming his boots, he's thrown them out," Frost said. "He's a great character for the group, a likeable guy that's cracking jokes and good for morale. He's good for our team culture and we'll get around him."

O'Donnell's injury came on a tough night in Wellington, the Brumbies falling in a physical encounter.

Larkham's side was up for the fight but the Hurricanes slowly wore their opponents away and took the upper hand in the second half.

Frost crossed for a double as Corey Toole continued to press his Wallabies claims with another electric performance.

While Jordie Barrett ensured the Hurricanes secured the victory, the Brumbies fought back late to claim a bonus point that could prove crucial late in the season.

Larkham shouldered some of the blame for the loss and said there were plenty of lessons to take out of the performance.

"It's obviously not the result we wanted," Larkham said. "It was a good kick at the end to take the [bonus] point. We were too inconsistent in multiple aspects of the game.

"Off the bye I don't think we got the training week right, some of the content as coaches wasn't where it needed to be. There were lots of mistakes, 20 for them, 17 for us, in wet conditions. It looked perfect but the dew was similar to Canberra in winter.

"Lots of different areas of the game weren't as consistent as they needed to be, which is something we're not happy about. All the players are disappointed but we also know we'll get a good review in on Tuesday into another big week. An Aussie derby against the Rebels is always a physical, confronting challenge."

WELLINGTON HURRICANES 32 (Devan Flanders, Ardie Savea, Cam Roigard, Aidan Morgan tries, Jordie Barrett 3 conversions, 2 penalty goals) bt ACT BRUMBIES 27 (Nick Frost 2, Rory Scott, Corey Toole tries, Noah Lolesio 2 conversions, Ryan Lonergan 1 penalty goal) at Wellington.

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