On a day of extended drama and fevered speculation, Novak Djokovic spoke publicly for the first time about being offered $200,000 (€183,000) to fix a match eight years ago though he vehemently defended his sport against accusers who allege match-fixing is widespread.

Djokovic and Serena Williams, the top-ranked players in the men's and women's game, were adamant there was no wrongdoing beyond minor incidents on the edges of the sport, and pointed out that no hard evidence had been produced.

The BBC, who conducted a long investigation in company with Buzzfeed News, has claimed an unnamed grand-slam winner was under suspicion, and that eight players who have been investigated during the past decade are in the main draw here.

They say they have a “cache of documents” stretching back to 2007 that expose, “widespread suspected match-fixing at the top level of world tennis, including at Wimbledon. Over the last decade, 16 players who have ranked in the top 50 have been repeatedly flagged to the Tennis Integrity Unit over suspicions they have thrown matches.”

After seeing off the exciting young Korean Hyeon Chung in three quick sets on the first day of the 2016 Australian Open, the defending champion Djokovic said: "I've heard about the story and I read that there were a couple of players mentioned who are not active anymore," he said, "talking about the matches that have happened almost 10 years ago. Of course, there is no room for any match-fixing or corruption in our sport. We're trying to keep it as clean as possible. We have, I think, a sport that has evolved, and have upgraded our programs and authorities to deal with these particular cases.

“I don’t think a shadow is cast over our sport. People are talking about names, guessing who these players are. But there’s no real proof or evidence yet of any active players, for that matter. As long as it’s like that, it’s just speculation.”

He spoke too about an incident in 2007 when it was alleged he had been offered $200,000 to throw a first-round match in Petersburg, a tournament he did not eventually attend.

“I was not approached directly,” he said. “Well... I was approached through people that were working with me at that time, that were with my team. Of course, we threw it away right away. It didn’t even get to me, the guy that was trying to talk to me, he didn’t even get to me directly. There was nothing out of it.

“Unfortunately there were some, in those times, those days, rumours, some talks, some people were going around. They were dealt with. In the last six, seven years, I haven’t heard anything similar. I personally was never approached directly, so I have nothing more to say about that.”

Pressed further he went on to say: “It made me feel terrible because I don’t want to be anyhow linked to this. Somebody may call it an opportunity. For me, that’s an act of unsportsmanship, a crime in sport, honestly. I don’t support it. I think there is no room for it in any sport, especially in tennis.

“I always have been taught and have been surrounded with people that had nurtured and, you know, respected the sport’s values. That’s the way I’ve grown up. Fortunately for me, I didn’t need to, you know, get directly involved in these particular situations.”

Ahead of what might or might not be explosive revelations on the BBC on Tuesday night, there was a sense here after the first day of the tournament that the only way these reheated claims will damage the sport is if players are named.

And, according to a senior source, that is highly unlikely. “I’d be surprised,” the source told the Guardian, “as they will potentially be in for huge libel issues. Unless they have evidence against them, they are on tricky ground.”

For most of the day, interest switched from the courts to the press conference room, where administrators and players were quizzed as if on a conveyor belt of suspicion and doubt. The most intriguing aspect of the allegations was the claim that a grand-slam champion was involved.

Marin Cilic, who won the US Open two years ago and on Monday progressed without fuss into the second round here by beating Thiemo de Bakker 6-7, 7-5, 6-2, 6-4, said he had never been asked to co-operate with match-fixers. "No, I never had any of that kind of situation and, even if i did, I would come forward to the ATP, to the people who are working for that."

He denied, also, that players were discussing the story in depth. “Not really, not that I know. This is a really high level of tennis, so it’s very difficult for me to see or to notice.”

Did the scattergun speculation, with any names so far, damage players across the board? “No, not for me. I know I am very far away from betting even though it is very popular in Croatia. A lot of people like to gamble, but I know I am safe, that I don’t do any betting. That’s very far away from me.

“I have big faith [in the game’s administrators]. They are the guys doing their job and I guess they are going it well. They know what they need to do to keep the sport the way it is. I have no idea [if match-fixing exists]. I hope not. That’s more a question for the integrity unit. But no, I don’t think it exists, not at this high level.”

Williams, talking after her tougher than expected 6-4, 7-5 win over the Italian Camila Giorgi, said: "Yeah, I just heard about it today, just as a warning that I might be asked about it. But that's literally all I have heard about it."

She had never personally heard of matches being fixed. “Not that I’m aware of,” she said. When I’m playing – and I can only answer for me – I play very hard, and every player I play seems to play hard. As an athlete, I do everything I can to be not only great, but historic. If that’s going on, I don’t know about it. I’m kind of sometimes in a little bit of a bubble.”

Kei Nishikori, who beat Philipp Kohlschreiber in straight sets, was suitably bewildered: "I didn't know anything. It's a little bit surprised, but, I mean, obviously I never, you know, involve with this. Actually I have no idea what's going on."

(Guardian service)