Heart problem was detected during spring physical exam.
The New York Mets say former pitcher Frank Viola is resting comfortably after heart surgery.
His children, Frank and Kaley, had said on Twitter that the 53-year-old Viola was scheduled for open-heart surgery Wednesday.
The pitcher retired as a player following the 1996 season. He was hired by the Mets in January as pitching coach of Triple-A Las Vegas of the Pacific Coast League, and a heart problem was detected during a spring training exam.
"I did talk to Frank yesterday," Mets general manager Sandy Alderson said Wednesday. "He certainly wants to be back, but I think we'll let the doctors dictate exactly when he comes back. When he's ready and he's able I'm sure he'll be out there, but we want to make sure he's fully recovered from this surgery first."
Viola was the 1988 AL Cy Young Award winner. He went 176-150 with a 3.73 ERA in 15 major league seasons with Minnesota (1982-89), the Mets (1989-91), Boston (1992-94), Cincinnati (1995) and Toronto (196).
His daughter Brittany was a diver on the U.S. team at the 2012 Olympics.