Zverev says behaviour was 'unacceptable' in Acapulco

German Olympic tennis champion Alexander Zverev said there "was no excuse" for smashing his racket on the umpire's chair several times and his foul-mouthed rant at the official was "unacceptable", as he was expelled from the Acapulco Open by the ATP.

Zverev, ranked three in the world, posted an apology posted on his Instagram account a few hours after his expulsion.

"It is difficult to put into words how much I regret my behaviour during and after the doubles match yesterday," he wrote.

"I have privately apologised to the chair umpire because my outburst towards him was wrong and unacceptable."

Zverev lost his cool after he and doubles partner Marcelo Melo of Brazil fell 6-2, 4-6, 10-6 to Briton Lloyd Glasspool and Finn Harri Heliovaara.

The 24-year-old defending singles champion smashed his racket three times just below umpire Alessandro Germani's feet before taking his seat and then rising again to shout at the official and smash the chair once more.

He had apparently been irked by a line call during the match.

Zverev had been involved in a marathon first-round singles clash with American Jenson Brooksby that finished at 04:54 local time   Tuesday morning, the latest-ever finish to a professional tennis match.

Zverev's mood may have been affected by fatigue after another long match in the doubles ended in defeat, but he nevertheless risks further punishment from the ATP.

"If the Senior Vice President Rules & Competition determines that the default was particularly injurious to the success of the tournament or detrimental to the integrity of the sport, he may consider additional penalties," reads the ATP rule book

Zverev said he would be reflecting on his behaviour.

"As you know I leave everything out on the court," he wrote.

"Yest