Roger Federer is the latest player to call for more drug testing in tennis.
Even though the 31-year-old former world No 1 believes tennis is fundamentally 'clean', he also thinks extended testing would send out a strong message to anyone thinking of messing with performance enhancing substances.
The winner of 17 Grand Slam titles, competing in this week's ATP Tour event in Rotterdam, said: "We should do more in terms of blood testing.
"I also support the biological blood passport, with information stored away. It's important to make sure that tennis is credible and clean to a maximum.
"We don't want players even getting the idea to cheat. Of course we need more funding.
"Maybe the Grand Slams should put in more since they have the most to lose if one of their players is not clean.
"I feel tennis is very clean, there's maybe one case a year and they are not all done on purpose. Some are just mistakes but stupidity can get you into trouble also."
Federer is top seed and defending champion at this week's indoor event which he also won in 2005.
World No 3 Andy Murray was another top player recently advocating more drugs testing in his sport.