Was worried about anti-doping rules, says Thiem on Red Bull outburst

New York - Thiem will now face 2014 champion Marin Cilic in the third round at US Open

World number three Dominic Thiem was visibly angry during his US Open second-round match against India's Sumit Nagal when officials told him that his energy drink could be provided to him in a cup.

On Thursday afternoon, officials told him that the can of Red Bull which he had asked for cannot be brought to court due to sponsorship reasons and so it was suggested that the drink could be poured into a cup off the court and brought to Thiem.

"Give me a plain cup, I'll somehow cover it and then I'll put it in," Thiem was heard as saying on court in between the sets. "You guys are crazy about anti-doping and then you want to carry the Red Bull can out and you guys fill it in a plain cup. What the heck is this? Bring me a plain cup please and I'll fill it in."

The can was then brought out and an official then covered it as Thiem poured it into the cup. Thiem later said in the post-match press conference that he didn't want the can to be poured into the cup out of his view and brought to him as that could have amounted to a potential anti-doping infringement.

"They wanted to go out with the open can and fill it in a plain cup without me observing it. That's what pissed me off a little bit because the anti-doping rules are so strict," the Austrian said.

"I don't want to lose the can out of my sight. In general, they are so strict rules these days, and they propose me to fill the can in a plain cup without me observing it. That pissed me off a little bit."

Thiem, who was celebrating his 27th birthday, won the match 6-3, 6-3, 6-2 against Nagal in the empty Arthur Ashe Stadium. He will now face 2014 champion Marin Cilic in the third round.