Tommy Haas has criticised the All England Club's decision to pay women and men equal prize money for the first time at this year's Wimbledon.
Haas progressed to the last eight in Memphis on Thursday
The German, ranked ninth in the world, said: "I don't think it's really fair.
"I think the depth of men's tennis is much tougher than the women's, plus we play best of five sets.
"Not to say the women don't deserve it. The top players train very hard and are very good players but in general I don't agree with it."
Following Thursday's announcement, Wimbledon will join the US and Australian Opens in paying equal money across the board, from the champions to the first-round losers in all events.
American Mardy Fish, like Haas speaking after playing at the Memphis International, said he understood the decision.
"We're all out there to put on a show for the fans," said Fish.
"OK, so we're not out there for the same time, the only beef I would have with it is that we're out there for longer.
It would be the only sport in the world like this, and will maybe make tennis appeal to more fans
"But there are a lot of tennis fans who prefer women's tennis to men's tennis. They have a lot of longer rallies and the fans like that - maybe the men's game is a bit fast."
Britain's Andy Murray said it was the right move.
"It's probably the only sport in the world where women are making the same money as men. That can really only be a good thing.
"Guys are obviously going to be annoyed if you go and play a five-hour match and then the women play a 45-minute match and they are getting the same money.
"But that's not really the point. Bar some of the top females, a lot of the guys get very good sponsorships.
"In the smaller tournaments, there's more money on the men's side, so apart from the Grand Slams, I think there are more tournaments on the men's tour as well."
"It would be the only sport in the world like this, and will maybe make tennis appeal to more fans, so for the four biggest tournaments in the year I guess it's a good thing."