Hopman Cup: Kyrgios injury flares

Two days after Nick Kyrgios stridently dismissed talk of lingering problems with his left leg he laboured through a dismal loss to Jack Sock at the mixed teams Hopman Cup in the tie between Australia and the United States.

Jack Sock of the United States (left) is congratulated by Nick Kyrgios of Australia after defeating him during their tenth session men's singles match on day five of the Hopman Cup.

Nick Kyrgios played down concerns over a worsening knee injury less than two weeks before the Australian Open in Melbourne.

Two days after the World No. 13 stridently dismissed talk of lingering problems with his left leg he laboured through a dismal loss to Jack Sock at the mixed teams Hopman Cup in the tie between Australia and the United States.

Kyrgios was beaten 6-2, 6-2 in under an hour in a performance which did not augur well for the Australian Open, starting a week from Monday.

In his first ATP tournament since serving a ban for tanking at the Shanghai Masters in October, the controversial Kyrgios served up another listless performance, barely moving around the court.

At one stage the 21-year-old inexplicably returned, from well beyond the baseline, a Sock shot which was sailing a long way out and dumped the forehand into the net.

After the loss Kyrgios pulled out of the scheduled mixed doubles and said scans on his left knee earlier in the day had revealed a problem, which almost led to him also withdrawing from the singles.

"It is not terrible but it is not great... just the start of some boney stuff in my knee," he said, "Obviously it was hindering me a little bit out there but I didn't want to do anything to make it worse.

"I just need to rest now and a couple of days without the load and I should be back to normal. I've got four days now to go home, see my physio, ice it and rest it and that is ample time for it to settle down."

Kyrgios, who had won his six previous singles matches in Perth over the last two Hopman Cups, was scheduled to play in two more exhibition tournaments in Sydney and Adelaide next week and said he still hoped to honour those commitments.

Regardless, Kyrgios said he would be ready for the Australian Open.

"I don't think losing in an exhibition Hopman Cup is going to hinder my performance too much for the Australian Open," he said.

"I'm not the type of guys who needs plenty of matches before a Grand Slam."

Sock dismissed comparisons with Kygrios' effort in Shanghai.

"I didn't see much of the Shanghai match, only highlights, but I think it is a completely different scenario," he said.

With Australia forfeiting the doubles, the United States beat the defending champion 2-1, although Daria Gavrilova beat Coco Vandeweghe, 6-3, 4-6, 7-5.

The Americans were already through to the final and will be hoping to give the US a record seventh title.

Sock and Vandeweghe will face either the Swiss pairing of Roger Federer and Belinda Bencic or the French combination of Richard Gasquet and Kristina Mladenovic.

The French and Swiss face off on Friday for the other spot in the final.