Nick Kyrgios came close to an upset victory over Roger Federer at the Miami Open last week. Photo: Geoff Burke-USA TODAY Sports
BRISBANE – The United States admitted on Thursday they are wary of the Nick Kyrgios factor in their quarter-final with traditional Davis Cup rivals Australia in Brisbane this week.

Kyrgios, the in-form world number 16, stands in the way of the USA team, all of whom are ranked in the top 30 in singles.

The mercurial 21-year-old comes into the clash in the form of his career after an epic, three-tiebreak-sets loss to Roger Federer in last week's Miami Open semi-finals.

He is drawn to face big-serving John Isner in the second singles rubber with Kyrgios winning their most recent meeting in the final of last year's Atlanta ATP event.

"Right now, a lot of people could argue he's playing maybe the best tennis he's ever played," the 23rd-ranked Isner said.

"Everyone knows what he can bring to the table. He's an incredible player but I'm a little bit used to the match-up.

"If our match does go to five sets I think it would make for a pretty cool atmosphere out there at the very least."

Kyrgios said he was banking on strong home support in Pat Rafter Arena against the Americans, after he battled a largely hostile crowd in his match with the popular Federer.

"I'm looking forward to getting back here and having some home support," Kyrgios told reporters.

"I think anything is possible this year. I feel comfortable playing second."

Rookie Jordan Thompson faces Jack Sock, the highest-ranked player in the tie at 15, in Friday's opening singles match.

Thompson, ranked 79 and preferred to the higher-ranked but out-of-sorts Bernard Tomic by captain Lleyton Hewitt, will be playing in the Davis Cup for just the second time.

The 22-year-old won both of his matches against the Czech Republic in February's first-round tie in Melbourne.

"The positive is that Jordan has been in this situation before," Hewitt said.

"He knew exactly what time he had to go out there and do all the right prep. It's going to be two tough matches on Friday but we'll be up for the challenge."

Thompson knows what he is up against to give Australia the crucial first point in the best-of-five match tie.

"He's got a great serve and a really big forehand. He's been in good form, I think he's up there with the most wins this season so far," he said of Sock.

Sam Groth and John Peers have been drawn to play Sam Querrey and Steve Johnson in Saturday's doubles before the reverse singles rubbers on Sunday.

It will be the 47th instalment of the most-played tie in Davis Cup history between the great rivals, with the Americans leading 26-20.