Sloane Stephens expressed concern with the way Wimbledon "judged" Bernard Tomic in fining the Australian his full prize money for a defeat to Jo-Wilfried Tsonga.
Tomic was fined $81,000 AUD after the match referee deemed he "did not meet the required professional standards" in a 58-minute reverse, the shortest men's match at the All England Club in 15 years.
The 26-year-old had similarly been punished for 'tanking' at Wimbledon in 2017.
Stephens, speaking after beating Wang Yafan in straight sets on Thursday, initially took offence to comparisons with Tomic's performances.
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"Really? I was going to say: you compare me to him? That's really messed up, bro," she told a reporter.
But the American then suggested Tomic's punishment represented a problematic "slippery slope", also referring to Anna Tatishvili's £41,000 fine following a 6-0 6-1 French Open loss to Maria Sakkari.
"I could see if he lost 6-0 6-0 6-0, then that would be something," Stephens said. "But he won four games, he played a 6-4 set.
A quick start for @tsonga7
— ATP Tour (@ATP_Tour) July 2, 2019
The charges past Bernard Tomic 6-2, 6-1, 6-4 to reach the second round. #Wimbledon pic.twitter.com/2zJrW2Yztz
"I don't know. I didn't see it. I have no idea. Obviously that happened at the French Open, as well. That was with Tatishvili.
"I think now if the tournaments are going to be their own judge and they're going to do that... hmm, I can't say I'm 100 per cent on board with that.
"With Tatishvili, I saw some of it, she lost [6-0 6-1]. But she played Sakkari. She's not playing a scrub. I just don't know if I can be down with that.
"And with the whole back story about her protected ranking and all that stuff, as well, like being forced to play basically or you lose it, there is a lot that goes into it.
"It's a very slippery slope, and when you start doing that and being the judge of what happens and how people earn a living, that's when it gets a little tricky."