Nick Kyrgios misses Davis Cup practice with a virus

Nick Kyrgios missed practice on Tuesday ahead of Australia's Davis Cup tie with the U.S., a virus preventing the world No. 26 from joining the hosts ahead of the first-round fixture at the historic Kooyong venue in Melbourne at the weekend.

Lleyton Hewitt insists, however, that he is unconcerned ahead of his debut as Davis Cup captain, saying he had ordered Kyrgios to steer clear of practising with his team-mates as a precaution.

"At the moment, he's taking it easy and trying to get over it 100 percent," Hewitt said. "I didn't want him around the boys if he's a bit infectious. Kyrgios has been in good form recently, claiming a "career-defining" victory in Marseille without dropping a set before advancing to the semifinals in Dubai the following week, when ESPN's Sandra Harwitt suggested he was "starting to take tennis seriously".

He withdraw from his semifinal against in Dubai, against Stan Wawrinka, with a back complaint, having carried a minor hip problem in France, but Hewitt said on Tuesday that those injuries didn't "seem to be a problem, which is very good news".

"He's played a lot of matches and both he and Bernie [Tomic] are confident coming in with their ball-striking.

"Come match day, I'm backing both those boys."

Bernard Tomic, Australia's top-ranked player, at world No. 20, hit the courts on Tuesday after a tricky transit from Mexico, where he had made the final in Acapulco.

Tomic, 23, is not without his own injury query, losing the decider against Dominic Thiem in Acapulco while taking painkillers for a troubled wrist.

He went straight to Kooyong within a few hours of touching down in Melbourne, we he said he would compete well even though he might be a touch short of full fitness for the tie. "I finished the final and had to fly five or six hours after that ... it was very tough to get here," Tomic said.

Tomic noted that had had the wrist injury "since I played [Andy] Murray in the Australian Open, I haven't pulled out anywhere, I've pushed through it.

"It's tough to say if I'll be at 100 percent but there's not going to be a lot of rallies; it's going to be a lot of quick points.

"I'm very happy the way I'm playing and I think I'll be very ready for sure on Friday.

"I'll give it with my heart and soul. I respect Davis Cup so much."

Kyrgios is expected at the courts on Wednesday, ahead of Thursday's team announcement, and U.S. captain Jim Courier expects to face a full-strength Australian team despite the Canberran's absence so far.