Former Philadelphia Phillies manager Charlie Manuel, who led the club to the 2008 World Series title, suffered a stroke Saturday.
The club said Manuel, 79, was undergoing a medical procedure in Florida when he had the stroke. Physicians were able to remove a blood clot.
"The next 24 hours will be crucial to his recovery, and Charlie's family asks that you keep him in your thoughts and prayers at this time," the team said in a release.
Under Manuel, the Phillies won five consecutive National League East titles from 2007 to 2011. They beat the Tampa Bay Rays in the 2008 World Series for the city's first major professional sports championship since 1983.
Philadelphia won another National League pennant in 2009 before losing to the New York Yankees in the World Series.
Manuel was fired by the Phillies in 2013 after the club got off to a 53-67 start.
He compiled a 1,000-826 record as a major league manager, including 780 wins with the Phillies. He was inducted into the team's wall of fame in 2014. Manuel rejoined the organization that year to work as a senior adviser to the general manager.
Reuters and The Associated Press contributed to this report.