Wildcards should not be given to players returning from doping bans, says world number one Andy Murray.
Russia's Maria Sharapova has been given wildcards for tournaments in Stuttgart, Madrid and Rome after her 15-month suspension ends next month.
"I think you should really have to work your way back," Murray told the Times.
"But most tournaments will do what they think is best for their event. If they think big names will sell more seats, they're going to do that."
Five-time Grand Slam winner Sharapova was banned for two years after testing positive for meldonium in January last year, but that suspension was reduced in October to 15 months following an appeal to the Court of Arbitration for Sport.
Wimbledon organisers face the potential dilemma of whether to hand the 2004 champion, who no longer has a world ranking, a place in this year's tournament in July.
"She has an opportunity to try to improve her ranking up until that point and potentially not need a wildcard," Murray said of Sharapova, who he played alongside at the International Premier Tennis League.
"But then if she doesn't, that becomes Wimbledon's decision and how they want to play that. I'm sure they'll think long and hard about it and how they feel people will view it and then make the right decision for them."