Australian firebrand Nick Kyrgios is well known for his temper tantrums, but the 21-year-old has promised to showcase his fun side when he lines up against Jack Sock in Thursday night’s Hopman Cup clash at Perth Arena.

Kyrgios knows Sock well after playing doubles with the American in the past.

The pair have formed a strong bond, and regularly hang out together at tournaments.

And with the US already guaranteed a spot in Saturday’s Hopman Cup final, there will be nothing on the line when the two pals lock horns in Thursday night’s dead rubber tie.

Kyrgios rates world No.23 Sock as a dangerman on the ATP tour.

The two rising stars could come up against each other in blockbuster grand slam matches in future years.

But it will mostly be about fun on Thursday night.

“He knows his game. He knows how to use it. I know it’s going to be tough,” Kyrgios said.

“But at the same time, it’s going to be easier to play him than the other guys, because the other guys take it really seriously.

“Jack and I get along pretty well off the court. So we’re going to have some fun out there.

“Obviously we both want to win. But at the same time, our first priority is to have some fun and keeping it loose out there for the crowd.

“I know what Jack’s going to bring. He’s got a big game, and he knows I’m going to bring it as well.”

Australia’s Hopman Cup title defence came to a grinding halt when they suffered shock 2-1 losses to both Spain and the Czech Republic.

Kyrgios has been in hot form during the mixed-teams event, winning both of his singles matches despite battling a minor knee injury.

But the same can’t be said for world No.25 Daria Gavrilova, who looked out of sorts in losses to world No.66 Lara Arruabarrena and world No.166 Lucie Hradecka.

Gavrilova has the chance to make amends on Thursday night when she takes on world No.36 Coco Vandeweghe.