US must be wary of fired-up Kyrgios - Tomic

Brisbane - Australia's No 2 Bernard Tomic will be absent from this week's Davis Cup quarter-finals but the United States will still have a fight on their hands in Brisbane due to the impressive form of Nick Kyrgios, US team captain Jim Courier said.

Kyrgios pushed Roger Federer to the limit in a classic Miami Open semi-final on Friday and beat world number two Novak Djokovic twice in succession in the recent US hard-court swing.

The 21-year-old firebrand will shoulder Australia's hopes at Brisbane's Pat Rafter Arena, with world No 79 Jordan Thompson retained for the singles while out-of-form Tomic continues his self-imposed exile.

Jack Sock and John Isner are expected to lead off the singles for the US team, who defeated the hosts at Melbourne's Kooyong Lawn Tennis Club in the first round last year.

"Nick has been playing some of the best tennis on tour already this season so he’s in great form and should have a lot of confidence," Courier told reporters in Brisbane.

"So we’re going to have to do something special to beat him.

"He's started off probably not the way he wanted to at the Australian Open, going out early, but since then he’s been a house on fire.

"So he’s playing right there, I mean, he's right there with Federer, and (Federer) has been the best player this season, so it’s impressive."

Kyrgios withdrew from last year's Kooying tie with a virus, leaving his replacement Sam Groth and Tomic to be ground down by the Isner-led United States on a purpose-built grass court at the former Australian Open venue.

Tomic opted out of this year's first round tie against an under-strength Czech Republic at the same venue, where Kyrgios and Thompson combined to lead the hosts to an emphatic 4-1 win.

Tomic, though currently in a dreadful run of form, has an impressive 17-4 record in Davis Cup singles and defeated Sock last year before losing the decisive tie to Isner.

Courier said opposing captain Lleyton Hewitt would miss Tomic's Davis Cup experience.

"He played last time we played down here and was awfully tough on us, so I’m sure it’s disappointing for Lleyton and the boys that he’s not involved this year," said Courier, whose team thrashed a Federer-less Switzerland 5-0 in the first round.

"But it’s not something that we know a whole lot about.

"We know that Jordan Thompson will be ready to battle ... There’ll be no easy outs for us."

The United States, who celebrated the last of their 32 Davis Cup titles in 2007, are bidding to reach the semi-finals for the first time since 2012.

A clash against either Italy or seventh-seeded Belgium awaits the winner.