Extraordinary moment ball boy catches ball while it's still in play at Australian Open – but it's what happened next that has left fans stunned

The fourth day of the Australian Open produced an extraordinary moment in the men's singles match between Karen Khachanov and Aleksander Kovacevic when one of the ball boys caught the ball on the net while it was still in play.

After winning the opening set 6-4, Khachanov faced a break point in the second set while trailing 2-1 when he fired a powerful serve off Kovacevic's backhand.

The 25-year-old American tried to get the ball back into play with a slice, but his looping attempt seemed to end up in the tram lines, which would have won Khachanov the point.

However, before the ball bounced and Khachanov approached the net to ensure it went wide, a ball boy caught it and the referee immediately called for the point to be replayed.

There were groans from the crowd as they realized what had happened, while Khachanov couldn't believe it as he told the referee: “It's here, where are the rules?”

A bizarre moment occurred during Karen Khachanov's (left) victory over Aleksander Kovacevic

A ball boy caught a ball hit by Kovacevic before it bounced as it appeared to go wide

As you can see from this angle, the ball went out of play as Khachanov chased the slice

Initially, the referee called for the point to be replayed, much to Khachanov's chagrin

An angry Khachanov protested to the referee as the Australian Open crowd cheered after the decision

The referee responded by telling Khachanov 'he has to let it bounce' as she explained that she had to stick to the rules and had no power to give the Russian the point.

But when she turned to her left, she saw Kovacevic gesturing to pass the point to his opponent.

It was a remarkable act of sportsmanship from Kovacevic, especially at such an important stage of the match, and Khachanov appreciated it as he raised his hand to thank his opponent, while still arguing with the referee after she initially called to determine the point. played again.

The referee confirmed Kovacevic's concession to the stunned crowd, which drew loud applause from those in the arena.

Khachanov then won the second set 6-3, before Kovacevic hit back in the third to make it 6-4 to give himself hope of a comeback.

But Khachanov held on in the fourth set, winning the set 6-3 and booking his place in the third round.

The 15th seed will be back in action in the last 32, where he will face unseeded Tomas Machac of the Czech Republic.