Tennis, Australian Open: Fear of being positively dope tested is stalking the men's locker-room, according to Albert Costa, the former French Open champion, who defeated Greg Rusedski 6-4, 6-3, 6-4 in the first round of the Australian Open yesterday.

"I promise you everybody is afraid, and everyone is saying, 'be careful'," said Costa.

Rusedski blamed defeat by the Spaniard on a bout of gastroenteritis over the weekend. "It wasn't the ideal preparation, hitting half an hour of balls coming into a major," he said. Neither was it ideal preparation having to admit to testing positive for nandrolone. There seemed little doubt the tribulations of the past 12 days had taken their toll, although he denied it. The British number two was patently jaded.

Now he must prepare for his independent tribunal hearing on February 9th. He hopes to get support from Bohdan Ulihrach, whose two-year ban was overturned last year, and the six unnamed players whose positive tests were dismissed by independent tribunals. "I'm hoping some will come forward and help me," said Rusedski.

Costa admitted he was "completely afraid" to take anything at all, save the drink he has used for six years. "For me, it was a big surprise when Greg tested positive. Maybe he took it, maybe he didn't. I'm not the person to judge him." Costa called for the ATP, the men's governing body, to set up a laboratory to test supplements, although the ATP has told all the players not to use any.

"But some still do," he said. "I never believed this could happen in tennis. I don't believe more than 40 players were taking nandrolone, and it may have been something in the food or water. I think our testing is good. Last year I was tested five or six times out of competition, and 10 or 15 times during tournaments. But I'm still feeling vulnerable."

It has been suggested Rusedski has continued playing in Australia to put pressure on the ATP, which would love to hush the matter up, having believed it had "solved" the nandrolone scandal with its internal inquiry after last year's rash of positives. Rusedski may be prepared to identify the anonymous six. If any are big names, it would be hugely embarrassing for the ATP. It is possible he and his lawyers are hoping for some sort of trade-off.

Not all the players are behind Rusedski. "When I saw Rusedski and [Juan Ignacio] Chela play each other on TV in Sydney I wanted to pull the plug out," said Belgium's Christophe Rochus. "They have both been caught and they still play like kings. It is shocking." Chela, of Argentina, failed a drugs test in 2001.

• Mark Philippoussis's cousin had a heart attack in a toilet during the Australian's win yesterday. The 10th seed, who beat Thomas Johansson 7-6 , 6-2, 7-6, said it was fortunate a doctor was at hand. He was unconscious when taken to hospital.