Former world number ones Andre Agassi and Andy Roddick have criticised the body that runs men's professional tennis for not taking a leadership role in the drugs furore engulfing the sport.
"The ATP needs to do something because...they've literally removed themselves from the problem and left the players out on their own," said Agassi, who is playing in the San Jose Open this week.
The ATP Tour has been embroiled in a drugs controversy since it emerged that trainers had been giving out nutritional supplements and electrolyte drinks that could have been contaminated and caused positive tests.
The ATP stopped giving out the supplements last May and an independent inquiry then cleared seven players who had recorded positive tests and overturned a two-year ban on Czech Bohdan Ulihrach.
British number two Greg Rusedski tested positive for nandrolone at a tournament in Indianapolis last July though the Briton, who had a drugs hearing in Montreal earlier this week, denied any wrongdoing and claimed he had been singled out.
Agassi, who said at last month's Australian Open that players were now "scared" about what they could and could not take, said on Thursday the tour was forcing too much responsibility on the players.
"I find myself as a player turning to the ATP and saying, 'Give us an answer.'
"There's no satisfactory answer I've received as to why the players are out there on their own in a media frenzy answering questions uninformed and being responsible for the integrity of our sport.
"That needs to come from our leadership and I haven't seen it yet.
"There has to be an answer somewhere. I'm not saying the answer is A or B, but the answer isn't to say it's not our problem, it's the players' problem."
ONLY WATER
U.S. Open champion Roddick said the tour also needed to take a leadership role, particularly given the schedule most players kept.
"In an international sport like ours, you can play one day in Asia and two days later in scorching hot weather in the States and you are supposed to drink water on the changeovers," said Roddick.
"That's a little bit of a stretch, no matter how good an athlete you are. You are going to need something to help, like vitamins.
"I'm not talking something crazy. When this question was asked at a player meeting, we got a 'we don't have that much for you, you're responsible for what you put in your body'.
"There's something that doesn't quite fit there. Right now it's kind of a rough situation because it's impossible to do what we do 46 weeks a year on water."