US Open champion Coco Gauff and French Open winner Iga Swiatek will miss next month’s Billie Jean King Cup finals.
The finals begin in Spain two days after the WTA Finals finish in Mexico.
World number four Jessica Pegula, who like Gauff is playing singles and doubles at the WTA Finals, is also missing from the United States team.
But Elena Rybakina of Kazakhstan and the Czech duo of Marketa Vondrousova and Karolina Muchova are planning to play both events.
Cancun was awarded the WTA Finals in early September – four months after Seville was announced as the host city for the Billie Jean King Cup finals.
Saudi Arabia and the Czech Republic had also been in the running to stage the WTA Finals, which feature the top eight singles players and doubles teams of the year.
The event will conclude in Cancun on Sunday, 5 November, with the 12-team Billie Jean King Cup finals beginning in Seville on Tuesday, 7 November.
Swiatek also missed last year’s Billie Jean King Cup finals in Glasgow, as the 2022 WTA Finals were scheduled to finish in Texas just one day earlier.
“I’m disappointed that tennis’ governing bodies did not 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,” she said 12 months ago.
“This situation is not safe for our health and could cause injury.”
Caroline Garcia, Madison Keys and Belinda Bencic – who will be the number one player for the defending champions Switzerland – are among the others who will be competing in Seville.