World number one Iga Swiatek on Monday joined Elena Rybakina in blasting late-night scheduling which wrecked the closing days of last week's Montreal Masters.

The four-time Grand Slam winner, who will chase her fifth title of the season this week in Cincinnati, said the WTA is taking little account of the physical needs of players when rain-delayed matches stretch into the early hours.

"Maybe we should focus more on what is healthy for players because we have to compete every week," the top-seeded Swiatek said as she awaited her second-round start here after a bye.

"The Tour is so intense with travel .. that it would be nice in the future to focus on players - especially next year when there will be more and more mandatory tournaments and longer tournaments."

The scheduling ordeal for last year's Wimbledon winner Rybakina began with a Friday night Montreal quarter-final against Daria Kasatkina which did not end until aronud 3am local time on Saturday.

Having won that encounter, the Kazakh had nothing left for a later Saturday semi which she lost in three sets to Liudmila Samsonova. 

Samsonova meanwhile was left having to play her semi-final and the final on the same day on Sunday due to weather disruption.

Rybakina complained afterwards about the physical demands of the scenario, with Swiatek backing her colleague to the hilt.

"During the clay season, in Rome and Madrid, I played four matches that finished close to or after midnight," Swiatek said.

"I understand we have to adjust to broadcasters and everything, but I also asked the WTA for some data to see if people are watching matches that start past 10 p.m.

"I didn't get anything, but it would be easier to actually understand that it makes sense to play that late."

Samsonova went on to lose the Sunday final to Jessica Pegula in 49 minutes.

Rybakina called WTA leadership "a bit weak now," adding: "Hopefully something is going to change because this year (there were) many (scheduling) situations which I cannot really understand.”

str/rcw