NEW YORK — Roger Federer said the doping case against Jannik Sinner raises questions about whether the current No. 1 in the tennis rankings should have been allowed to continue playing until he was cleared of intentionally using an anabolic steroid for which he tested positive twice in March.

“It’s not something we want to see in our sport, this kind of news, regardless of whether he did something or not. Or any player. It’s just noise that we don’t want. I understand the frustration of: Was he treated the same as others? And I think that’s what it comes down to. We all trust that ultimately he didn’t do anything,” Federer said Tuesday in an appearance on the “Today” show to promote a book of his photos. “But the inconsistency, potentially, that he didn’t have to be offside when they weren’t 100 percent sure what was going on — I think that’s the question that needs to be answered here.”

A few hours later on Tuesday evening, Federer received a warm round of applause from the crowd at Arthur Ashe Stadium as he was introduced to the crowd during the second set of the US Open quarterfinal between Aryna Sabalenka and Qinwen Zheng.

Federer smiled and waved as he was shown on the video boards around the arena.

It was the 20-time Grand Slam champion’s first visit to the venue since retiring from competing. Federer announced his retirement in 2022; he played his last official match at Wimbledon the year before.

He is the last man to win back-to-back US Open titles, having won five in a row between 2004 and 2008.

Several top players have been asked about Sinner, who will face 2021 US Open champion Daniil Medvedev in the quarterfinals of the Grand Slam tournament on Wednesday.

Rafael Nadal told a Spanish television program on Monday that he does not believe Sinner received preferential treatment.

The International Tennis Integrity Agency reported on August 20 that it had determined that the banned performance-enhancing drug had inadvertently entered Sinner’s system through a massage by his physiotherapist. For that reason, the player was not suspended.

“I understand the frustration of, was he treated the same as others? … We all trust that ultimately he didn’t do anything. But the inconsistency, potentially, that he didn’t have to be sidelined when they weren’t 100 percent sure what was going on — I think that’s the question that needs to be answered here.”

Roger Federer

When asked about the issue in New York ahead of the US Open, Novak Djokovic said he understands why some tennis players wonder if there is a double standard in the sport.

“It’s a difficult situation and a nightmare for any athlete and any team to have to deal with these allegations and issues,” Federer said, adding: “We have to have confidence in the process and in the process of everyone involved.”

Federer said he recently spoke with Nadal, his longtime rival on the court and friend off it, who is 38 and has played sparingly the past two seasons because of injuries, including hip surgery last year. He is sitting out the US Open.

There are questions whether Nadal, who has won 22 Grand Slam trophies, will return to the tour.

“He can do whatever he wants,” Federer said. “He’s one of the most iconic tennis players we’ve ever had in our sport. … I just hope he can leave on his terms and in the way he wants.”