Federer's brilliant reaction to female opponent's winner

Anastasia Pavlyuchenkova left the great Roger Federer completely stunned with a brilliant winner at the Hopman Cup.

Federer led Switzerland to a 3-0 sweep over Russia on Tuesday night, but Pavlyuchenkova got the biggest cheer from the crowd during the mixed doubles.

Pavlyuchenkova managed to produce a stunning volley in the third set that not even Federer could track down.

The Russian star picked up the ball from off the deck and pulled off a wonderful angle to win the point.

Federer could only look on in awe as he lost the point, his mouth agape at Pavlyuchenkova's brilliance.

As for Pavlyuchenkova, she threw her arms up in triumph, drawing a raucous response from the record Perth Arena crowd.

The brilliant moment was reminiscent of one earlier in the tournament when Japan's Naomi Osaka managed to ace Federer with an amazing serve.

Federer and Belinda Bencic are undefeated after two rounds and will take on USA next, with the winner of Thursday night's showdown progressing to the final on Saturday.

Federer is confident his blockbuster clash with Jack Sock will go ahead despite the American's injury concerns, with Sock retiring hurt with a hip injury in his clash with Japan's Yuichi Sugita on Tuesday.

"I think he'll be fine," Federer said of Sock.

"There was no reason for him to take a major chance on his health so short before the Australian Open (in his match on Tuesday).

"We'll see all the players having this kind of a thought moving forward in the next 10 or 12 days, because you don't want to get hurt now.

"I think he should be OK with a day's rest. At least I hope so."

with AAP