"I have been in contact with Felix and he and his family are safe," Mariners spokesman Tim Hevly said by email.
No one was hurt and there was no immediate information on the cause of the fire.
Hernandez and his wife, Sandra, were in Napa, Calif., when the fire started but were returning to Seattle because of the blaze, his agent Wil Polidor told The Seattle Times. The agent said the couple's two children were at a mall with their nanny and the pitcher's mother-in-law when the fire started.
Firefighters from nearby Redmond and Mercer Island joined Bellevue crews to attack the blaze.
Bellevue Fire Department Lt. Richard Burke told The Times that most of the "substantial damage" to the house was on the first floor while the second floor was mostly damaged by smoke. Burke did not immediately return phone and email messages from The Associated Press.
King County public records show the 5,100-square-foot, five-bedroom, four-bath house belonging to Felix A. and Sandra Hernandez. It was built in 2009 and is valued at $2.85 million.