London (AFP) - Roger Federer has warned tennis chiefs they must bring in tougher measures to weed out drug cheats in a bid to avoid a repeat of the Russian athletics doping scandal.
Russia has been accused of "state-sponsored" doping by an independent commission set up by the World Anti-Doping Agency (WADA) in a report which has stunned the sporting world.
The shocking revelations could eventually lead to Russian athletes being excluded from the 2016 Rio Olympics.
Swiss great Federer, speaking in London ahead of his appearance in the season-ending ATP Tour Finals, is a firm believer in testing players as a deterrent, but the 17-time Grand Slam winner is adamant his sport can do more to stamp out drug issues.
"I think it's very important. The player needs to feel that there are going to be tests often to shy them away from the stupid thoughts they might be having," Federer told reporters at London's O2 Arena on Friday.
Tennis' anti-doping programme falls under the jurisdiction of the International Tennis Federation and the exact amount spent on it is not made public.
And Federer believes the sport's bosses have the resources to ensure players are tested after every match once they reach the latter stages of tournaments.
"I think they try their best but I think we could always do more. We have a very clear thing of what we should be doing -- more testing," he said.
"In my opinion where the points become greater, the money becomes greater and we need to be tested. It is very simple. That's how you scare off people.
"I don't understand that sometimes you have a run and you win a couple of events, and the next thing you know you haven't been tested. It just can't be that way.
"I'm always surprised when I win a tournament, I walk off the court and it's like, 'Where's the doping guy?' I don't get that. I hope in the future it's going to be better."
- Hardline stance -
While world number three Federer takes a hardline stance, Novak Djokovic, the reigning Tour Finals champion and world number one, has a different view.
Djokovic launched a stinging attack on the anti-doping programme at the Tour Finals in 2013 after his fellow Serb Viktor Troicki was given a 12-month ban for missing a doping test.
On Friday, Djokovic backed the doping programme but criticised the 'whereabouts' policy for being too strict.
Athletes have to inform the testers of where they will be for a period each day to enable random out-of-competition testing.
"The whereabouts demands are a little bit too much and a bit unnecessary to write where you are every single day of the year," Djokovic said.
"If you don't appear at the place where it is written down then you get a warning, then two warnings and then suspension. I think that is a bit too much.
"The tennis season is very long. They know where we are and they can find us.
"When you're in the off-season you are going back and forth and changing cities and locations and it can be hard to track down and fill in the whereabouts sheet."