Disgruntled Djokovic refused a doping test before his Davis Cup quarter-final match

"I've never experienced something like that before," said Djokovic, who beat Great Britain's Cameron Norrie 6-4, 6-4 in the quarterfinals to secure a 2-0 win for his team.

The Serbs will face Italy in the semifinals on Saturday.

"They came to me an hour and a half before the match when I was already preparing for the match and I don't have time to think about giving blood or urine.

"So I argued with them because I have never experienced something like that in my 20-year career," he added.

"The commissioner then sat in the corner and watched me for hours. It was unbelievable.

"I've always stood up for inspections, but not before games. I have nothing to hide, but there should be some boundaries," Djokovic added.

The winner of a record 24 Grand Slams finally submitted to the scrutiny after the match.

However, according to Marca newspaper, pre-match checks are common at ITF events and the captains of all eight participants in the final Davis Cup tournament were informed in advance.