Rafael Nadal has joined the chorus of disapproval over the ATP’s failure to take action regarding Andre Agassi’s admission that he took drugs in 1997 and lied about the circumstances to avoid a ban.

“If the ATP covered for Agassi at the time, then I think that’s dreadful,” Nadal, the world No 2, said in Madrid yesterday. “The only thing I can say is that if they covered at that moment for the player and punished others for doing the same kind of thing, then that would seem to me to be a lack of respect for all sportsmen.”

On being told he had tested positive for crystal meth, the banned stimulant, Agassi said that he wrote a letter to the ATP claiming that he had taken it by accident and asking for leniency. No disciplinary action was taken.

Roger Federer, the world No 1, also voiced his disappointment, but said that Agassi had done a lot for the sport “as a player and as a human being”. The Swiss said: “It was a shock when I heard the news. I am disappointed and I hope there are no more such cases in future. Our sport must stay clean.”

Martina Navratilova also expressed her shock. “Andre lied and got away with it,” the 18-times grand-slam singles champion said. “You can’t correct that now. Do you take away a title he wouldn’t have won if he had been suspended?”

Agassi at least found some support from Andy Roddick, the Wimbledon men’s singles finalist this year. “Andre is and always will be my idol. I will judge him on how he has treated me and how he has changed the world for [the] better,” the American wrote on his Twitter page.

Meanwhile, in Doha, Piotr Wozniacki was pumping his fists and Anna, his wife, peered through her fingers as Caroline, their daughter who is surely destined for great things in this sport, writhed on the floor of the Centre Court at the Khalifa Complex last night.

Caroline was not to know that she was only five points from the end of the match that more or less secured a place in the semi-finals of the Sony Ericsson Championships, nor were her mother and father, whose greater concern was if their teenage offspring was going to do herself serious damage. She had to get up and continue, because she had already had one medical timeout and had been visited twice more by the trainer.

Vera Zvonareva, her Russian opponent, tried to extend the ensuing points as long as she could, torturing the 19-year-old Dane. It says much for the fortitude of the US Open runner-up that she emerged with her second victory in two days — the first, against Victoria Azarenka, of Belarus, lasted a minute short of three hours; this one was two hours and 48 minutes.

Wozniacki won 6-0, 6-7, 6-4 and has to play Jelena Jankovic, of Serbia, today with mathematics in her favour but still not totally assured of a place in last four at the weekend. Zvonareva, a late replacement when Dinara Safina, her compatriot, pulled out of the championship on Wednesday with a back injury, has done her bit for the year and can go home and rest.

There was much concern about Wozniacki at the end of the match. Even with a late afternoon start, it is very warm for late October. Copenhagen, it isn’t.

“When it was 3-1 for me [in the final set] I got the cramp in my leg,” she said. “From there, it just got worse and worse. I have absolutely no idea how I pulled it through. I’m gonna do everything I can to get ready for tomorrow. I’m just going to do everything that the physiotherapist and the doctors are saying: drinking a lot of fluids, eating some good food, stretching, get some massage, get some ice massage, take a salt bath, everything.”