Canada's Eugenie Bouchard in doubt for Australian Open after buttocks injury at Hopman Cup

Former world No.5 Eugenie Bouchard hopes her Australian Open campaign won't be derailed by a buttocks injury picked up at the Hopman Cup.

Bouchard looked out of sorts at the mixed-teams event, losing all three of her singles rubbers.

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And the 23-year-old suffered an untimely injury scare on Friday when she injured her buttocks during the second set of her 6-4 6-4 loss to Belgium's Elise Mertens.

Belgium secured the tie win after world No.7 David Goffin beat Vasek Pospisil 6-2 6-4 in 82 minutes.

And they were awarded a 3-0 clean sweep after Bouchard pulled out of the mixed doubles.

West Australian Maddison Inglis filled in for Bouchard in the mixed doubles.

"My arse hurts," Bouchard said after her singles match.

"I think it's maybe a little strained or a little pulled or something.

"There was a really sharp pain. I felt it going wide on my backhand and landing on my serve with my left leg.

Canada's Eugenie Bouchard receives treatment on her injured buttocks at the Hopman Cup. (AAP)

"I'm going to the physio now to see what it is. I don't think it's too bad but it was getting worse throughout the match."

Bouchard, who is due to fly out of Perth on Friday night to compete at the Hobart International, was hopeful rather than confident the injury wouldn't affect her Australian Open hopes.

"I'm hopeful but you never know," she said.

"You always get little muscle pulls here or there but this one specifically, no (I've never had it before)."

Even though Belgium won the tie 3-0, Germany are in the box seat to reach Saturday's final.

They are yet to be defeated at the mixed-teams event and will qualify for the decider with victory over Australia on Friday night.

If Germany lose, then Belgium will scrape through.

Switzerland's pairing of Roger Federer and Belinda Bencic have already secured their spot in the final by topping Group B.

"We did the job, so that's the most important thing. We are going to watch tonight and hopefully Australia can win the match," Goffin said.

Mertens required treatment on her eye during her win over Bouchard but she said it wasn't anything serious.

"There was some sunscreen in my eyes," she said.