Nick Kyrgios left fuming after Daniil Medvedev's run-in with a fan

Nick Kyrgios has come out to bat for Daniil Medvedev, defending his tennis rival after he was heckled by a fan for no reason.

Kyrgios and Medvedev have a fiery past with both men clashing both on and off the court.

But despite all that, Kyrgios couldn't help but leap to his rival's defence after witnessing what he described as "disgusting" behaviour.

In the clip posted on social media, world No.1 Medvedev can be seen leaving the arena at the Canadian Open following his 6-7(1) 6-4 6-2 loss to Kyrgios.

As Medvedev emerges to sign autographs and take pictures, one fan's voice can be heard above the crowd calling him a 'loser'.

Medvedev walked up to the man to confront him but security swarmed the area to ensure tempers didn't flare too much.

The pair did exchange a few pleasantries, although it's hard to make out exactly what was said from the footage.

Upon seeing the exchange, Kyrgios took to Twitter to show his support for Medvedev while also condemning the spectator's actions.

"Disgusting behaviour," Kyrgios tweeted.

"This is the best we have in the sport, fans need to show some respect."

The original caption for the video read: "God, how awful can fans be when they chant ‘loser’ to a tennis player after a tough battle on the court Achieve something yourself in this life.

"Having respect for another person is an important rule of a human being."

Speaking after his recent victory over Medvedev, you can see the respect Kyrgios has for the Russian as a player.

“I’ve had some success against him in the past and he’s beaten me before so I feel like we know each others’ games well,” Kyrgios said after the match.

“I’m not the type of player who goes into these matches looking at rankings or anything like that.

“It’s just who I’m playing and what kind of ball they’re giving me and today I had a very clean objective of how I was going to play – a lot of serve and volley, a lot of aggressive play from the back – and I executed better than he did on the day.

“That’s all it came down to. He won the first set and I feel like I had opportunities there as well so hopefully I can keep this rolling.”