Roger Federer has claimed that there is not a "major problem" with illegal drug-taking in tennis, but believes that the authorities need to do more in the wake of Maria Sharapova's failed test.
The Russian pro was provisionally suspended by the International Tennis Federation after testing positive for banned substance meldonium at the Australian Open in January.
Federer, who is a 17-time Grand Slam champion, believes that tennis is not riddled with players using performance-enhancing drugs, but wants testing increased.
The 34-year-old revealed that he has only been tested once in Dubai, where he owns a property, over the past 10 years, while in his homeland of Switzerland he is tested regularly.
"Clearly, I was very surprised [about Sharapova] - I thought she was going to announce her retirement, but it also shows that the famous players can get caught in the system," Federer told reporters in a press conference at the Miami Open.
"It seems to be working. I still believe we should keep blood samples for 10 years, so athletes and tennis players know that's the case, that you could get punished retroactively. I'm a big believer in that.
"I don't think [there's a drug problem in tennis]. Maybe I am naive in the fact that I believe athletes, I trust what they are doing. Clearly, when they get caught you turn because you are like: 'I can't believe that they tried to do that'. I don't think there is a major problem, all I can talk about is myself. I quadruple check anything I take. I don't want to take any chances whatsoever."
Federer has marked his return to action in Miami following knee surgery.
