But, to the delight of the Old Trafford faithful, the Scot was pictured smiling on his first public appearance since the operation at his former haunt ahead of United's clash with Wolves.
Sir Alex Ferguson looked thrilled to be back in his seat at Old Trafford on Saturday afternoon but fans were even happier to see him.. I'm gradually making steps forward, doing what my surgeon tells me and the doctors tell me so, yeah, I'm really good.
Ferguson, 76, who was in intensive care for several days at Salford Royal Hospital earlier this year, will take his usual seat in the directors' box for the game.
The last time Ferguson attended a game at Old Trafford was in April, when he presented outgoing former Arsenal manager Arsene Wenger with a commemorative gift. "It was a long time but it's great to be back". It had to happen some time and I've been looking forward to it.
"It's bound to be emotional". He underwent emergency surgery at Royal Salford hospital.
Asked about the messages of support he had received, Ferguson added: "It was unbelievable". That will be something, you know.
"Paul enjoy the night, sorry I'm not there to enjoy the celebration, well done for a fantastic career and being a great human being". I'd left by that time but they kept coming and kept coming.
'I'm overcome by it and overwhelmed by it.
"Thank you from me and my family, thank you very much". It was really important to do that. And some of the doctors who did the operation are here too - I thought it was the right thing to do. "It's great to be back!".
The legendary former Manchester United manager - who won 25 major trophies during his 26 years as Red Devils boss - was taken ill in May after suffering a brain haemorrhage.
Manchester United host Wolves after winning two away games in a row in the league, and after running out victorious against Young Boys in the first game of the Champions League group stage.