The incident happened during their round one Australian Open fixture when the pair were tied 4-4 in the fifth set.

Klizan managed to lob a weak return to Wawrinka before seemingly surrendering the point, only to have the ball scorched at his nether-region.

He dropped to the court in agony prompting Wawrinka to jump the net and console his opponent.     

Wawrinka eventually won 4-6 6-4 7-5 4-6 6-4 after making an uncharacteristic 43 errors.

Klizan spoke of his disappointment at his Swiss opponent’s ball placement. 

"I stopped playing. He could play anywhere, the whole court," the Slovak said.

"He could play anywhere on the court and he hit me."

The 2014 Australian Open champ said he did not intend to hurt his defenceless opponent.

"That was, for sure, a tough shot for him. The thing is there are some players they fake you, and you stop playing and then they just put up the racquet," Wawrinka said.

"So for me I already miss some easy ones. For me the most important thing was to run straight over to him.

"I just wanted to make sure he was OK. I realised he was OK.

"I'm sorry I touch him in the wrong place. But I think it was OK at the end."