Sir Alex Ferguson left Old Trafford ahead of Manchester United's Premier League clash with Liverpool on Sunday after feeling unwell and was taken to hospital for precautionary checks, sources have told ESPN.
The 84-year-old former United manager arrived at the stadium before the game, but travelled to hospital in a non-emergency scenario before kickoff after receiving medical attention.
Ferguson, who retired in 2013, regularly watches the club's matches from the director's box.
United's legendary manager took over the team after leaving Aberdeen in 1986, leading the club to 13 Premier League titles and two Champions League triumphs. In total, he lifted 38 trophies in his 1,500-game United tenure as the team established itself as English football's dominant force.
Ferguson suffered a brain hemorrhage in May 2018, and after surgery, he received a standing ovation when he returned to Old Trafford the following September.
On Sunday, United held off a Liverpool fightback with Kobbie Mainoo's 77th-minute goal sealing a 3-2 win that means the club will play in the Champions League next season.
United head coach Michael Carrick was asked about Ferguson's health after the match but was unable to provide any updates on the condition of his former manager.
"I haven't got any updates. I did hear about it before the game so I was aware of that. All I can say is I was affected," Carrick told a news conference.
"We wish him all the best and hopefully the result gives him a good boost."
Information from PA, the Associated Press, and ESPN's Mark Ogden contributed to this story.