Sinner overcomes slow start to reach US Open second round amid doping cloud

:Top-seeded Italian Jannik Sinner shrugged off the doping furore surrounding him and overcame a bad start to reach the second round of the U.S. Open with a 2-6 6-2 6-1 6-2 victory over American Mackenzie McDonald on Tuesday.

Sinner became embroiled in controversy in the week before the year's final Grand Slam after the International Tennis Integrity Agency said that he tested positive twice for an anabolic agent in March.

The Australian Open champion, who has denied wrongdoing, has been under intense scrutiny in New York so far and was slow out of the starting blocks.

He committed several unforced errors in the opening set, which McDonald took full advantage of to claim an early lead.

The American broke early in the second set to take a 1-0 lead, but after spurning three breakpoints in a lengthy game, Sinner levelled at 1-1.

The hard-fought break appeared to fill the world number one with confidence and the tide of the contest turned as he raced to a 4-1 advantage, before holding serve and breaking once again to square the match at a set apiece.

Sinner never looked back from there and won five games in a row to take the third before winning the first three games of the fourth set without dropping a point.

McDonald won a couple of games late in the match to delay the inevitable, but Sinner made his advantage count and served out the set to claim an emphatic victory.

"It started not in the best way, but you know, the first matches in every tournament are not easy, you have to accept it," Sinner said in his on-court interview.

"He played really, really well in the beginning and I tried to stay there mentally and tried to get into rhythm, which I've done at some point in the second set and then just tried to keep going. I'm very