Mourinho left three years later but returned to Chelsea for just over two years before the love affair soured in December 2015. His former charges are one of four London sides in the last eight.
There is a certainty that at least one of them will be in the semi-final as Tottenham Hotspur take on Millwall.
Arsenal should also advance too. They host fifth division Lincoln City at the Emirates. But the Arsenal boss, Arsene Wenger, leads his men into the fixture with his future appearing more fragile than at any point during his 21 year reign in north London.
Fans protested about his stewardship of the club outside the Emirates before the second leg match against Bayern Munich on Tuesday in the Uefa Champions League.
Trailing 1-5 from the first leg in Munich, even the most faithful of Arsenal's fans probably knew that progress past the German champions into the last eight was unlikely. What they would have expected though was pride in the performance.
And that yearning was rewarded mid-way through the first half when Theo Walcott scored, igniting hopes of a comeback. But it was a brief moment of happiness in the general drama of pain that has engulfed the Wengerian landscape.
A penalty that could have made it 2-0 to Arsenal was not awarded. And in the second half, the Germans racked up five goals following the dismissal of Arsenal defender Laurent Koscielny.
A 5-1 score line for Arsenal against Lincoln City on Saturday afternoon might pacify some of Wenger's critics. But even victory at Wembley in the FA Cup final in May might not save him.
"Because of the way the game has changed, there are only two competitions that really matter," said Kevin Whitcher, editor of the Arsenal fanzine The Gooner. "And they are the Premier League and the Champions League.
"So, yes winning the FA Cup is fantastic, but it's not what it used to be in terms of its kudos and its meaning because the priority is different for clubs and supporters. And you can see that by the types of teams managers field in the FA Cup."
Wenger, 67, is wily enough to know that sending out a team of youngsters against Lincoln would be a very public resignation letter, even though Arsenal face a fight over the last 11 games of the Premier League season to assure their participation in next season's Champions League.
On paper, Manchester City are favourite to beat Middlesbrough. But both sides have their eyes on other prizes. City, leading 5-3, face Monaco on Wednesday for the second leg of their last 16 tie in the Champions League and Middlesbrough, in 18th, have 11 games to secure their Premier League status.
Tottenham should simply have too much firepower for Millwall and Chelsea against holders Manchester United could provide fireworks.
When United visited Stamford Bridge in October for their Premier League showdown, Mourinho criticised his successor Antonio Conte for inciting the crowd when Chelsea were 4-0 up.
"No, there is nothing we have to clarify with him," said Conte ahead of Monday night's clash at Stamford Bridge.
"I've shown at Chelsea, not only Chelsea, every team that I managed that I live the game with great passion. Sometimes I want to share my enthusiasm, my passion with my players, with my staff, also with my fans. I think it's normal."
But obviously not for a Special One.