Nick Kyrgios and girlfriend Costeen Hatzi arrive at Sydney Airport after Japan Open

Nick Kyrgios and Costeen Hatzi are back in Australia after a trip to Japan.

The pair looked gloomy when they arrived at Sydney Airport, after the tennis champion withdrew from the Japan Open minutes before the quarterfinals.

Costeen, 22, and Nick, 27, were greeted on arrival by Costeen’s family, who helped them with their luggage.

Nick dressed casually in a black hoodie and gray sweatpants and white sneakers.

He was carrying a backpack and drinking a cup of coffee as he walked with a serious expression on his face.

Costeen, meanwhile, opted for a candy pink hoodie and tight leggings along with black and white socks and sneakers.

She covered herself with a surgical face mask and also had a cup of coffee and a beige tote bag.

Nick said he was devastated to withdraw from the Japan Open with a knee injury, just minutes before taking on Taylor Fritz in the quarter-finals.

Kyrgios, who had his eye on two titles in Tokyo and had also reached the doubles semi-final with Thanasi Kokkinakis, withdrew from both events on Friday night.

“It’s heartbreaking, when the body lets you down it’s not a good feeling,” the Wimbledon finalist told reporters at the Ariake Colosseum Arena.

“I’ve played fantastic tennis all year, but I had a knee problem around the US Open and came home, probably didn’t take enough time to be honest, and went straight back to training,” Kyrgios said.

“I played well this week, probably (the knee problem) could have something to do with the surface change.

“But my knee is something I’ve dealt with my whole career and sometimes it wakes up pretty average and when I was warming up with Thanasi it just didn’t feel ideal.

“Take off is the smart option for my body. I have a few more events to go in the year and I want to do it right. So I have to be smart.

“But of course very disappointing, it’s one of my favorite tournaments, I have great memories here.

‘I know that in this case it’s more about overload than not being fit enough. I think it’s almost too excited to get on the field and maybe training a little too much. It’s positive but heartbreaking at the same time.’

Kyrgios flew home to recover before he planned to finish the season in tournaments in Basel, Paris and the season-closing ATP finals where he and Kokkinakis hope to add to their Australian Open crown.