It is a mark of the interest in Lance Armstrong's confession, however limited it was in detail, that, even halfway around the world, most of the talk in Melbourne yesterday was about the American and not about what happened on the court.

Novak Djokovic continued his imperious progress at the Australian Open as he downed Radek Stepanek of the Czech Republic 6-4, 6-3, 7-5 but it took just four questions of his post-match press conference before the talk came round to what everyone wanted to know: what did he think about Armstrong?

"I haven't seen the interview, but I heard he was admitting it," Djokovic said. "I think everybody was expecting him to do that. It would be ridiculous for him to deny all the charges because they have like a thousand [pages of] proof that he [tested positive for drugs].

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"I think it's a disgrace for the sport to have an athlete like this. He cheated the sport. He cheated many people around the world with his career, with his life story. I think they should take all his titles away because it's not fair towards any sportsman, any athlete. It's just not the way to be successful. I think he should suffer for his lies all these years."

A quick walk round the media centre and the players' restaurant here revealed many laptops tuned into Armstrong's confession to Oprah Winfrey. Drugs in tennis is a thorny issue, as in many sports, and there are often many disparate voices but, as the world No.1, Djokovic's is listened to more than most.

The Serb, who is chasing a third consecutive Australian Open title and fourth overall, revealed he had not been blood-tested out of competition for six or seven months. "It was more regular in the last two, three years," he said. "I don't know the reason they stopped it. We're trying to protect the identity of this sport. I believe tennis players are some of the cleanest athletes in the world, so as long as we keep it that way, I have no complaints about testing."

As in all sports signed up to the code of the World Anti-Doping Agency, tennis players have to give drug testing authorities a location and one-hour slot where they will be every day, three months in advance.

Djokovic, like many players before him, highlighted the scarcity of positive tests in the past few years as evidence the system is working, but in 2011 only 21 blood tests were carried out by the ITF, 18 on men and three on women.

The high cost of the test, around $1000 a sample (about £627), is one reason given for the low number but the ITF say they are planning to increase the number carried out over the next few years. "I have nothing against the blood tests, even though I prefer urine tests," Djokovic said. "I don't like the needles too much. But of course the money should be invested in that direction because it's a safeguard that is going to protect our sport and players."

"[In cycling] I think it's not acceptable that they have so many races in a short period of time. I think basically every single day, or day and a half, they have to go ride 200 miles, uphill, downhill, in the Giro d'Italia, Tour de France; that's an inhuman effort. As you can see, Lance Armstrong and many other big champions had to use something to succeed."

During yesterday's match, Stepanek enjoyed himself on the big stage but Djokovic was in a different league. The third set was close, but he did what he needed to do to advance, reaching round four without losing a set.

In an era when the semi-finals and finals of grand slams have produced a number of epic encounters, saving your energy early on is crucial and Djokovic was delighted no to over-exert himself.

The No.4 seed, David Ferrer, wore down Marcos Baghdatis 6-4, 6-2, 6-3 while Tomas Berdych, the fifth seed, was equally impressive in beating Jurgen Melzer 6-3, 6-2, 6-2. Janko Tipsarevic, seeded eighth, needed five sets to get past Julien Benneteau of France, though, eventually coming through 3-6, 6-4, 2-6, 6-4, 6-2.