The two-time Wimbledon champion Petra Kvitova suffered severe injuries to her playing hand defending herself from a knife-wielding intruder in her apartment, an attack she said left her "fortunate to be alive".
The tennis world number 11 is having surgery on the hand and its unclear no indication when she might be able to play again.
"In my attempt to defend myself, I was badly injured on my left hand," she said on her Twitter account @Petra_Kvitova. "The injury is severe and I will need to see specialists, but if you know anything about me I am strong and I will fight this."
Kvitova was attacked in her flat in the city of Prostejov, about 260 km southeast of Prague, the site of a tennis club where she, men's world number 10 Tomas Berdych and other top-ranked Czech tennis players train.
Karel Tejkal, spokesman for the Czech Fed Cup team, told Czech media the morning attack had been "a random criminal act" and she had not been specifically targeted.
The Czech Republic won the Fed Cup, the premier national team competition in women's tennis, for the third year in a row in November.
The website of newspaper Mlada Fronta Dnes said the intruder presented himself to Kvitova as a boiler inspector.
"What has happened to me was not pleasant at all, but it is already behind me," she said in an earlier statement issued on the Fed Cup team's Facebook page.
"The main thing for me now is that the doctors will determine how my hand is doing. I trust them and I believe that it will end well."
The hard-hitting left-hander has been a near constant in the world's Top 10 since 2011, rising as high as number 2 that year, when she won the first of her two Wimbledon singles titles.
She slipped in the rankings this year but showed improved form in recent months, winning the Wuhan Open title in October and the season-ending WTA Elite trophy in November.
In 1993, then-world number 1 Monica Seles was stabbed courtside during a break at a tournament in Germany by a man who admitted having an obsession with her rival Steffi Graf.
The attack forced Seles out of tennis for two years.