The International Tennis Federation (ITF), and professional tennis as a whole, has zero credibility when it comes to making claims of a being a "clean sport" or having "strict doping controls." The more likely situation is widespread doping in the sport. Why? The reasons are plenty:
Because the ITF
doesn't appear to have issues with professional tennis players working
with personnel that have been banned for anti-doping violations. (see also this article)
Because Stuart Miller, the head of the ITF anti-doping program, believes "It may be that tennis is not conducive to EPO..." and that "tennis is not obviously lending itself to a particular category of performance-enhancing products."
Because Francesco Ritti Bitti, President of the ITF believes that when it comes to doping: "Many cases are due to simple ignorance by the players."
Because under Stuart Miller, blood testing by the ITF decreased by 33% between 2006 and 2011.
Because under Stuart Miller, EPO testing by the ITF decreased significantly between 2006 and 2009.
Because under Stuart Miller, the ITF anti-doping program is underspending its budget.
Because, leading up to Beijing Olympics, the ITF conducted 79% of their out-of-competition tests after the Games.
Because, in 2009, 49 out-of-competition missions by the ITF resulted in "no sample being collected," including Federer, Nadal, V. Williams, S. Williams, Roddick, and Wozniacki.
Because, at Grand Slam events, the ITF conducts loser-targeted testing.
Because, at non-Grand Slam events, the ITF typically doesn't conduct doping tests beyond the early rounds.
Because the ITF allows top players to go multiple years without an out of competition doping tests.
Because the ITF conducts minimal out of competition tests compared to other sports.
Because the ITF reduces anti-doping suspensions for no apparent reason.
Because top players actively promote Omerta.
Because the ITF actively prevents other anti-doping organizations from testing at ITF events. (also read this)
For the reasons above (and more), the ITF anti-doping program is either completely inept, or deliberately designed to not catch players doping. There do not appear to be any other obvious explanations. Such an anti-doping regime has, on the balance of probabilities and lessons from history, likely resulted in widespread doping in the sport.
As a result, ALL tennis players have a cloud hanging over their heads. If they want this to change, they should take it up with the ITF and the tennis media. And if the tennis media wants this to change, they should take it up with players and the ITF. Depending on the true state of affairs, it may very well be that a Truth and Reconciliation Commission is the only way to clean-up the sport.