A day after former manager Alex Ferguson underwent emergency surgery for a brain haemorrhage, Manchester United tweeted: "Please. Be strong. Win this one."
The online post, which provided no update on the 76-year-old Ferguson's condition, came 21 hours after United announced that Ferguson required "a period of intensive care to optimise his recovery."
One of Ferguson's greatest rivals, Arsene Wenger, took time out of his Emirates Stadium farewell to send his best wishes to the Scot.
"Before I start I just want to say that at Arsenal we care and I would like to wish my fellow manager Ferguson well, very quickly," he said.
Ferguson's most recent public appearance came last week at Old Trafford when he made a presentation to Wenger ahead of the Frenchman's final tussle with Manchester United.
Social media continues to be awash with tributes and get-well messages for Ferguson, who spent almost 27 years in charge before retiring in 2013 as the most successful manager in British football history.
Among those sending their best wishes was Manchester City manager Pep Guardiola before he received the Premier League trophy that Ferguson won 13 times.
"A big hug and our thoughts are with his wife, Cathy, and the Manchester United family," Guardiola said. "I was glad to have dinner with him two weeks ago, and hopefully he can recover as quickly as possible."
Huddersfield boss David Wagner said after his side's goalless draw with Manchester City: "I only got the message yesterday very late.
"I'm very sorry for him and his family and I wish him all the best that he recovers as quick as he can. It was a shock, for sure, when I heard it. All my thoughts are with him and his family."