Sources told Klein that Cox was home alone Tuesday afternoon and went to a neighbor's house after he started to feel unwell.
Braves manager Brian Snitker told The Associated Press on Wednesday morning that he had reached out to Cox's family and was "very concerned." He said he couldn't share details of Cox's condition. The team has not revealed Cox's medical status.
On Wednesday, WSB-TV sports director Zach Klein said in a tweet that Cox had surgery to remove a blood clot. The tweet also said that the stroke has impacted his speech and right side of his body.
Cox served 25 years as manager of the Braves. He has been considered the ultimate players' manager.
Cox retired from the Braves in 2010.
In 2014, he received baseball's highest award. He was inducted into the Baseball Hall of Fame, along with two of his big three starting pitchers, Greg Maddux and Tom Glavine.
Cox led the Braves to 14 consecutive division titles from 1991-2005, including the World Series championship in 1995. Over his career, he managed 4,505 games and compiled a 2,504-2,001 record (.556).
Cox was a four-time manager of the year, winning in both the National and American Leagues.
Cox has served in a front office position with the Braves following his retirement.
The Associated Press and The Atlanta Journal-Constitution contributed to this report.