An Atlanta Open crowd has booed Nick Kyrgios off court after he retired mid-match in his quarter-final against Cameron Norrie with a hip injury.

The Australian second seed was trailing the British left-hander 7-5 3-0 after 52 minutes of play when he decided he could not continue.

At times Kyrgios, 23, seemed disinterested in the contest with his effort in question late in the opening set before he meekly double-faulted to give Norrie the early break in the second.

Nick Kyrgios saw the trainer midway through the first set but that did not prevent the crowd booing him off court at the conclusion.

The last time Kyrgios played in Atlanta he defeated then three-time defending champion John Isner to claim the title.

Kyrgios suffered a hip injury at Queen’s in early 2017 and has struggled with it ever since. Photo: AAP

Earlier in the tournament, Kyrgios had told reporters if he was playing at his best it would be “tough to lose” in the quarter-final against Norrie.

“I always feel comfortable playing here … the court suits my game style,” he said.

“If you’re playing well and you’re seeing the ball well and you’re serving well, it’s tough to lose here.”

Kyrgios had described the left-handed Norrie as a “tough competitor”.

“He’s always been a tough competitor … he’s a tricky player, he’s a lefty, great backhand,” Kyrgios said. “Lefties are always tough on a surface like this.

“I’m going to go out there, nothing’s going to change on my end. I’m going to serve big, play big and we’ll see how it goes.”

Matt Ebden will fly the Australian flag in the last four after he required just 71 minutes to defeat Marcos Baghdatis.

The Australian world No.55 broke the Cypriot’s serve three times to secure a comfortable 6-3 6-2 win over the former Australian Open finalist.

Ebden is through to his second tour-level semi-final of the year as he strives for his maiden ATP Tour title.

The 30-year-old has not dropped a set in Atlanta but will face a stern test next when he faces top seed John Isner for a place in the final.

The American was pushed to three sets by German sixth seed Mischa Zverev before he prevailed 7-5 4-6 6-1, dropped just two first-serve points in the match and sending down 21 aces.

Ebden is 1-3 against Isner but won their past meeting in January at the Australian Open.

-with AAP