Nick Kyrgios vents frustration as he exits Australian Open warm-up event

Nick Kyrgios admits there is a “massive question mark” hanging over his Australian Open credentials as he battles a knee injury and ongoing mental hurdles leading into the grand slam.

Kyrgios was up to his usual tricks in a straight-sets defeat to Croatia’s Borna Coric in a warm-up event at Melbourne Park on Friday, mixing some brilliant play with a mid-match dummy-spit.

The 25-year-old firebrand was warned by the chair umpire during the second set of his 6-3, 6-4 defeat, after smashing a racket and hurling it into the largely empty grandstand.

He also vented his frustration over the blustery conditions on the outside court and ongoing pain in his troublesome knee, which he said flared up last year and has not fully settled.

“There’s a massive question mark for me, even if I was completely healthy, [after] not playing in a year,” Kyrgios said. “It’s not easy to just turn around and prepare for an event just like that. It’s not like a tap.

“I thought I did everything I could this week. I won a couple of matches, I had a lot of court time and practised every day, as well. I think I’m ticking the boxes, I think I’m giving myself a chance.”

Friday’s result, which brought Kyrgios’s Open preparation to a halt, came less than 48 hours after he stormed off the court and called the chair umpire a “smartarse” during his win over Harry Bourchier.

Kyrgios said his mental state is more important than anything and that he will use a few days off to refresh before his Open first-round match. “If I’m positive and motivated, I’m sure I’ll play some good tennis,” he said.

Compatriot No 1 Ash Barty’s successful comeback has continued, with the women’s world No 1 surviving a third-set shootout to advance to the semi-finals of her warm-up event at Melbourne Park.

Barty edged American Shelby Rogers 7-5, 2-6, 10-4 in a deciding match tiebreak on Friday to set up a last-four blockbuster with 23-times grand-slam winner Serena Williams.

Clutch under pressure, Barty raised her game in the cut-throat breaker after losing five games in a row to drop the second set.

“I feel like I did well to hang in there at times and then Shelby was able to hit me off the court during other times,” Barty said. “It was an important start to that third-set tiebreak in a bit of an unusual sort of scoring system for us. But I’m happy to get through and get another opportunity tomorrow.”