Mourinho enjoyed two spells in charge at the club and is the most successful manager in Chelsea's history, having won a total of eight trophies.
His most recent tenure at Stamford Bridge ended in December 2015 after a tumultuous start to the club's Premier League title defence, ultimately paving the way for him to join United the following May.
This season, Mourinho's past with Chelsea has become something of a sideshow to his feud with Antonio Conte.
After the United boss dragged up Conte's ban for match-fixing earlier in his career – for which he was later acquitted - the Italian responded by labelling Mourinho a "little man" and a "fake".
He was careful not to reignite things two days before the match at Old Trafford, however, before downplaying the significance of his meetings with Chelsea.
"I don't want to speak about it, not at all," Mourinho said of his previous spat with Conte during Friday's pre-match news conference.
"Very good manager, fantastic team and that's what is important for me. It's just that.
"For the past 10-15 years, Manchester United versus Chelsea have been big matches," Jose says. "We are both fighting for the top four, but it is always a big game, regardless of what’s at stake."#MUFC— Manchester United (@ManUtd) February 23, 2018
"To play against Chelsea will mean less and less and less with the years. Of course, I left already a couple of years ago and next season it will be three years ago, then four years after that.
"Step by step that feeling I was the Chelsea manager, for them, I think this disappears, so the real meaning of this game is it is two big clubs playing one more match."
Despite his somewhat fractious relationship with current Chelsea coaching staff and fans, Mourinho remains on good terms with the club's board.
He said: "I have a good relation with the board. I don't forget how nice they were to me in a difficult period when my father departed.
"They showed they see me as a friend, as someone who did his best and respected the club, so in relation to the board, they know the relationship with me is always good.
"With the players I don't have any problems, any regrets, any stones in my shoe, no problems at all and the fans are fans. With many of them in the streets I feel that empathy, a relationship that normally should be a connection forever.
"When I play at Stamford Bridge, some rejections from fans are just reactions."