The ACT Brumbies are refusing to panic despite suffering a last-round meltdown in Perth and missing a chance to gain momentum before the Super Rugby finals begin.

The Brumbies will play their first finals match in nine years when they take on the Free State Cheetahs at Canberra Stadium next Sunday afternoon.

But the disappointment of a shock loss to the Western Force in the last game of the regular season will linger in the lead up after the Brumbies lost 21-15 at nib Stadium.

Just a couple of months ago the Brumbies demolished the Force 41-7 at Canberra Stadium.

Everyone expected a similar result, especially given the Brumbies had a chance to rise into the top two on the ladder and the Force had won just three games all year.

But for whatever reason, the Force dominated and the Brumbies failed to show up ready to play.

ACT coach Jake White insisted his team could bounce back in time to be a title contender and beat the Cheetahs at home.

"I'm not sure what to say other than it looks like whenever we play the last round of a competition we don't know what we're doing," White said.

"I just said to the players that we have to try to win every single game. We were probably guilty of thinking about [the finals] and I guess we're just thankful we can get away with a loss here.

"If you're going to lose a weekend, you'd rather lose this one. It's going to be a wake up call, we know we can't get any worse [than the way we played against the Force]."

The Brumbies finished the regular season third on the overall ladder and winners of the Australian conference.

Failing to finish in the top two makes their path to the championship even harder.

They must first account for the Cheetahs and then face a trip to South Africa to take on the Pretoria Bulls.

The Brumbies haven't played the Cheetahs this season because of the way the Super Rugby draw has fallen.

The Bloemfontein-based team's travel from South Africa and the Canberra Raiders' game against the Parramatta Eels on Saturday night means the match will be played at 4pm on Sunday.

It gives the Brumbies extra time to recover from the demoralising trip to Perth.

Prior to the match the Force was second last on the ladder and had won just three games all year.

The Brumbies should have been the team desperate to win with the finals looming.

But the visitors were out-enthused and lacked energy.

The Brumbies scored just three points in the first half and trailed 21-3 just after half-time.

They rallied to get back within six points with 12 minutes remaining after tries to Tevita Kuridrani and Scott Fardy.

But in the end it was fruitless as the Force held on to finish their season on a high.

"It's been a very difficult year for lots of reasons," Force coach Michael Foley said.

"There was such a bleak feel from last season, the players pulled together strongly and learned to play together.

"This was a season we weren't going to win a lot of games and that's challenging for players ... to get this result [against the Brumbies] means the players have learned a lot about what they're capable of."

The Brumbies' loss was punctuated by uncharacteristic errors.

Fullback Jesse Mogg - who was backing up after making his Wallabies debut - had a shocker. The Brumbies dropped the ball 17 times in the game. Conditions were tough, but 17 errors is unacceptable.

The Brumbies never looked like they were in the contest as the Force powered on and scored three tries.

The win wasn't without controversy. The Force's first try came from a Matt Hodgson quick tap, but the skipper failed the release the ball when it touched his foot before he barged over the line.

For the second try, scrumhalf Alby Mathewson didn't take his quick tap from the correct mark.

When the Force crashed over for a potential match-winner in the second half, the television match official should have ruled Ben McCalman was inside the five metro line when he took a short lineout.

Instead, the TMO awarded the Force an attacking scrum five metros out from the Brumbies line.

The Force were still deserved winners, but the victory was tempered by Hugh McMeniman being taken from the field on a stretcher with a neck injury.

The Brumbies' horror night was summed up perfectly when flyhalf Matt Toomua failed to ground the ball inside his own in goal before throwing a pass out to the 22metre line for the restart.

"Mentally we were just that little bit off and at this level you can't do that," Brumbies captain Ben Mowen said.

"The Force won the attitude and work rate areas ... it was probably a good night to have in terms of you can't just assume you can turn up and it will happen.

"So much of this year has been really good. We're not going to change things now, it's just about mentally being in the right frame of mind. Maybe we were guilty of thinking it would just click."