Former Test fullback Cameron Shepherd bagged a hat-trick to help Matt Giteau make a triumphant return to Canberra Stadium in a stunning Western Force 25-16 Super 14 upset of the Brumbies on Saturday night.

The win was the Force's first in Canberra and only the Brumbies' second ever home loss to an Australian side in their Super rugby history.

Shepherd's triple confirmed his return from a horrendous broken ankle suffered playing for the Wallabies against France in Brisbane last July after he had missed last week's win over the Cheetahs still suffering soreness.

It also relieved some of the pressure on the Perth side, which had been reeling from superstar five-eighth Giteau's decision to quit the franchise at season's end, and rumours of discontent between players and coach John Mitchell.

Instead, the Force got the perfect start to a three-match road trip that will see them take on New Zealand sides the Chiefs and Crusaders in the next two weeks.

The Force and Brumbies have now both won two of their first three games of the Super 14 season.

Returning to Canberra for the first time since his announcement, Giteau had a hand in two of Shepherd's five-pointers, but could only kick two from six in the four tries to one bonus point win in front of 15,893 fans.

With his side down 6-0, Shepherd touched down in the 27th minute after Giteau had sent Ryan Cross steaming through a hole.

The Brumbies led 9-8 at halftime through Mark Gerrard's boot but Shepherd scored just four minutes after the break after some quick hands, with Giteau throwing the final pass.

When No.8 Richard Brown scored the Force's third try in the 50th minute after a strong run from Junior Pelesasa, the Force were suddenly up 20-9.

But when a series of bulldozing attacking scrums from the Brumbies resulted in a penalty try, a grandstand finish was ensured at 20-16, despite the away side having scored three five-pointers.

Shepherd gave the visitors some breathing space again in the 68th minute with his third and the Brumbies couldn't find the execution to seriously threaten again.

"You can't ignore that Cam came back from a very serious injury and he'd be probably the first to acknowledge that he's walked slowly into the competition," Mitchell said.

"We must take our hat off to him tonight, he played with an enormous amount of confidence and his penetration in one on ones was quite outstanding."

Mitchell deflected any suggestion Saturday night's win was a season-defining one for the under-fire Force.

"It's too early to say," he said.

"This is a tough competition and wherever you can pick up points is crucial.

"We did ask the question this week to step up in our game and I think we got a big tick for that."

The Force's season hadn't started well with a limp loss to the Hurricanes and a narrow win over the struggling Cheetahs.

Mitchell said the added blow of Giteau's announcement hadn't added to the pressure.

"It didn't really feature in our preparation or camp this week at all so it certainly wasn't distraction," he said.

Brumbies coach Andy Friend lamented his side's flatness.

"I thought our scrum and lineout were very, very good but just our energy levels and our ability to control the football wasn't good so we need to work on that," he said.

"We need to find some answers to that, as to why we were flat and slightly off."

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