Iga Swiatek warned the tennis schedule is "not safe" and "could cause injury" as she pulled out of the Billie Jean King Cup Finals.
The world number one was due to represent Poland in an event that will be staged in Glasgow from November 8-13, but withdrew on Monday.
That competition will start just a day after the WTA Finals finish in Fort Worth, Texas.
US and French Open champion Swiatek criticised governing bodies the WTA and International Tennis Federation (ITF), who run the Billie Jean King Cup, over the calendar.
"I was thinking it through a lot and discussing it with my team, but I will not be able to play at the Billie Jean King Cup in Glasgow," Swiatek posted in an Instagram story.
"It makes me sad. I'm very sorry, because I play for Poland whenever it's possible and I always give it my best.
"Playing in Poland this year [in the qualifiers] was an honour and I hoped to do this again at the end of the season.
"I'm disappointed that tennis governing bodies didn't come to an agreement on something as basic as the calendar of tournaments, giving us only one day to travel through the globe and changing the time zone.
"The situation is not safe for our health and could cause injury."