World number one Jannik Sinner insists that fans have been "positive" in their response to his doping test controversy but he will tackle his locker room critics face-to-face rather than engage in a public slanging match.

Sinner marked his return to the courts for the first time since it was revealed he had failed two drugs tests, coming back from a set and break down to defeat Mackenzie McDonald at the US Open.

Italian Sinner battled to a 2-6, 6-2, 6-1, 6-2 win over his 140th-ranked opponent on Arthur Ashe Stadium, racing away with 18 of the last 22 games.

The 23-year-old was returning to action just a week after news broke he had failed two dope tests in March.

However, he escaped a lengthy ban from the sport when officials decided he wasn't at fault for the presence of banned anabolic agent clostebol.

Sinner argued that the drug entered his system when his physiotherapist used a spray containing it to treat a cut, then provided massage and sports therapy to the player.

Australian Open champion Sinner has since fired physio Giacomo Naldi and trainer Umberto Ferrara -- who supplied Naldi with the spray -- citing a loss of confidence in them.

"The response from fans, I feel it has been great, also throughout when the news came out, in the practice sessions, there was a lot of support," said Sinner.

"It's still a little bit not easy. You have to go through day by day."

However, some players have aired their unease at the decision by the International Tennis Integrity Agency to clear Sinner of wrongdoing.

Australia's Nick Kyrgios said in a post on X that the lack of a suspension was "ridiculous".

Canadian player Denis Shapovalov said the decision proved that there are "different rules for different players" suggesting that Sinner was saved by his ranking and status as a Grand Slam winner.

"I cannot really control what they think and what they talk. I cannot control the players' reaction," said Sinner.

"But if I have something to say to someone, I go there privately, because I'm this kind of person."

Victory on Tuesday was a first win for Sinner on the showpiece Arthur Ashe Stadium.

"The support is amazing, let's see what's coming," added Sinner who has endured a rollercoaster relationship with the US Open.

Twelve months ago, he was defeated in five sets by Alexander Zverev in the last 16 while in 2022 he was knocked out by eventual champion Carlos Alcaraz in a five-set quarter-final which finished just before 3 a.m.

Sinner will face Alex Michelsen of the United States for a place in the third round.

Carlos Alcaraz roared home 

PHOTO: AFP

Carlos Alcaraz roared home for a 6-2, 4-6, 6-3, 6-1 victory over 186th-ranked Australian Li Tu on Tuesday to launch his bid to add the US Open to the Roland Garros and Wimbledon titles he claimed this year.

The 21-year-old Spaniard pushed his Grand Slam winning streak to 15 matches as he tries to join Rod Laver and Rafael Nadal as the only men in the modern era to win the French Open, Wimbledon and the US Open in the same year.

He got off to a hot start, seizing a 4-0 lead on the way to pocketing the first set.

But Tu, who came through qualifying, got to grips with the imposing Arthur Ashe Stadium and Alcaraz's serve to take the second set.

He tried to keep the pressure on in the third, but Alcaraz's break for a 4-3 lead opened the floodgates, the Spaniard winning the eight straight games to take the third set and build a 5-0 lead in the fourth.

But Tu wouldn't go quietly, saving a pair of match points before Alcaraz closed it out with a love service game.

"Obviously it surprised me a little bit," Alcaraz said of Tu. "The first set it was obvious that he started the match nervous.

"But after the first he started to enjoy, to play really great tennis. I was playing great -- probably a few mistakes," added Alcaraz, who had 50 winners and 30 unforced errors.

The third-seeded Spaniard, who won the first of his four Grand Slam titles in New York in 2022, will face Botic van de Zandschulp in the second round, headed toward a possible semi-final showdown with top-ranked Australian Open champion Jannik Sinner.