MELBOURNE -- Back in 2007, someone tried to offer Novak Djokovic roughly $200,000 to lose a first-round match at a tournament in St. Petersburg, Russia, he said Monday at the Australian Open.

Djokovic said he wasn't approached directly. Instead, "I was approached through people that were working with me at that time," he said, making clear that the offer was flat-out rejected. He didn't even attend the tournament, but he said he still didn't like the fact that someone even bothered to consider him for such a thing.

"It made me feel terrible because I don't want to be anyhow linked to this kind of -- you know, somebody may call it an opportunity," he said. "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."

A number of players reacted to the BuzzFeed/BBC report that says there has been widespread match-fixing in men's tennis and that authorities in the sport ignored it. The report did not name players because a direct link to betting could not be proved, but it said there is a core group of 16 suspected men who have been ranked in the top 50, including a US Open champion, involved.

"I would love to hear names," Roger Federer said. "Then at least it's concrete stuff and you can actually debate about it. Was it the player? Was it the support team? Who was it? Was it before? Was it a doubles player, a singles player? Which slam? It's so all over the place. It's nonsense to answer something that is pure speculation. Like I said, it's super serious and it's super important to maintain the integrity of our sport. So how high up does it go?"

While Federer questioned how many new developments were in the story -- much of it is about the 2007 match scandal involving Nikolay Davydenko and Martin Vassallo Arguello -- he said he hopes this will put more pressure on the governing bodies to take such things seriously. "Hopefully there's more funding to it," he said. "Same as doping. Yes, absolutely, got to be super aggressive in both areas."

Djokovic said there were rumors of match-fixing in the past and that they were dealt with but that he hasn't heard of anything in the past six or seven years. Serena Williams said she wasn't aware of any match-fixing incidents, either.

"I can only answer for me. I play very hard, and every player I play seems to play hard," she said. "I think that 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. You know, I'm kind of sometimes in a little bit of a bubble."

Federer said if he heard someone was offered money to fix matches, he would encourage him to go to the tennis authorities. If the player did not, he would.

"He needs to feel he's been supported by the tour, or whatever the governing body is, that there's a place he can go and speak about it," he said. "It's uncomfortable, not a fun thing. It's not like, 'Oh, I've just been approached, it's all cool,' and we don't talk about it. I think it's really important that you get supported and get also told how to manage that.

"So, yes, I guess I would encourage that person to go and say something. Otherwise, I would say something or I would encourage us to go together."

Another issue to this story is that the Australian Open has a sponsorship deal with the William Hill gambling company, and there is advertising signage for the company at Melbourne Park. Some wonder how is it proper to take money from a gambling company and encourage fans to bet if the sport truly wants to keep players from fixing matches.

"This is a subject for discussion, I think, today and in the future," Djokovic said. "It's a fine line. Honestly, it's on a borderline, I would say. Whether you want to have betting companies involved in the big tournaments in our sport or not, it's hard to say what's right and what's wrong."

Federer said that in some way the sponsorships are connected and other ways they are not.

"Betting happens all across the world in all the sports," he said. "The players just need to know, we need to make sure the integrity of the game is always maintained because without that, why do you come and watch this match tonight or any match? Because you just don't know the outcome. As long as we don't know the outcome, the players, fans, it's going to be exciting. The moment that gets taken away, there's no point anymore to be in the stadium."