Switzerland's Stan Wawrinka, left, checks on Slovakia's Martin Klizan after he was struck by the ball during their first round match at the Australian Open in Melbourne on Jan 16, 2017. [Photo/IC]

Stan says he's sorry

Meanwhile, Stan Wawrinka apologized for slamming a ball at Martin Klizan after he survived a tense five-setter to reach the Australian Open second round.

Wawrinka, a three-time Grand Slam champion, fought back from a break down in the final set to overhaul the 35th-ranked Slovak 4-6, 6-4, 7-5, 4-6, 6-4 in a match that lasted three and a half hours.

There was a dramatic moment in the final set when Wawrinka fired a volley at a defenseless Klizan, who had conceded the point after a rally and was standing at the net.

The Swiss fourth seed quickly jumped over the net to offer his apologies as Klizan sunk to his knees in pain.

"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 racket," Wawrinka said.

"I had already missed 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."

Klizan preferred not to pass judgement on Wawrinka but said the Swiss could have hit his volley anywhere on the court.

"I stopped playing. He could play anywhere, the whole court," the Slovak said. "He could play anywhere on the court, but he hit me."