Iga Swiatek and Emma Raducanu have pulled out of next week's Billie Jean King Cup qualifiers for their respective teams.
Poland is hosting Switzerland and Ukraine in the round-robin qualifier but Swiatek, who is ranked No. 2, said Wednesday she made the "difficult decision" to skip it.
"I always represent my country with pride. I played everything there was to play for the country last year," Swiatek said in a statement. "Now it's time for more balance, focusing on myself and my training."
Swiatek lost to wild card Alexandra Eala in the Miami Open quarterfinals last week. The five-time Grand Slam champion had also been given extra security protection at the tournament after being verbally attacked during a practice session by a man who had sent her harassing messages via social media.
Also Wednesday, Britain's Lawn Tennis Association announced that Raducanu has withdrawn. Britain plays Germany and the Netherlands in The Hague.