The tennis governing bodies encourage players to dope
I don't mean this in the literal sense, nor do I support doping for any reason. However, I believe the tours, tournament directors, the ITF, expect way too much from today's players, yet they also expect them to be sqeaky clean.
Tennis players are expected to be tougher than 300 pound NFL linemen in many ways. They don't get to sit on a "bench," and they don't get any sort of coaching (which can be mentally stressful). If a player cramps during a 5 setter, people start claiming he is not fit enough. Commentators often assume a player is faking an injury if they take time out, so basically, tennis players are supposed to gut it out, even if they are in more pain than a woman in labor.
On top of that, the ATP schedules back to back 64 draw Masters Series events (Rome/Hamburg), (Canada/Cincy), and penalize guys who skip any of these events! Plus, the guys who run themselves ragged during the claycourt season either skip Wimbledon all together (and get criticised for it) or they play the grasscourt season with little or no recovery time.
It doesn't stop there either. The ATP schedules a lucrative tourney in China the day after the US finishes and plenty of the top names show up. And this one tops the rest of them: by holding the USO sf's and f's in consecutive days, the USTA believes that all the top men SHOULD be able to play 10 sets in two consecutive days! And of course, there is no offseason and the only way guys can have offseasons is by sitting out important events like Davis Cup, Masters Series events and even Slams.
Meanwhile, this sends a message to all the top players that they better be able to recover easily in order to survive the season. Yet when anyone goes through a Slam, winning several 4-5 set matches and looks fresh as a daisy, people assume they are doping!!!
How can the governing bodies insist the players stay clean and then give them the most grueling schedule of any sport?
The force will be with you, always.