Croatia's Ivo Karlovic, well-known for his thundering serves, is recovering in hospital in Miami after being admitted with viral meningitis, his wife Alsi said.
In a statement on the official ATP website (www.atpworldtour.com) she dismissed reports that the 34-year-old had suffered a stroke.
"Ivo did not have a stroke, as some outlets have stated; rather, he has viral meningitis," she said.
"We ask for privacy during his recovery process. We thank everyone for their support and well wishes."
Karlovic, who has slipped outside the world's top 100 from a career high 14, caused one of the biggest upsets in tennis when he beat defending champion Lleyton Hewitt at Wimbledon in 2003. He last played at the Sarasota Challenger earlier this month.