"Just shut up and sign", was the Manchester United manager's very public recommendation to his Belgian midfielder. Mourinho was joking. Well, half-joking. The delays, which had run for weeks, baffled Mourinho. But there was a confidence this deal would be done.
But now? Well, there was a hint of resignation in his comments last week. The same type of concession which he'd been fielding from those involved in negotiations on United's side of the table.
"Is he going to stay or leave? I don't know," admitted Mourinho. "I want him to stay, the club want him to stay. The process – negotiations, numbers, distances between the offer and what he wants – I really don't know."
This is new ground for Mourinho. Players don't leave the Special One. They leave United, sure. Cristiano Ronaldo. Patrice Evra. Jaap Stam. They all left Old Trafford with still plenty to give. But no-one leaves Mourinho. Well, not until now.
We can talk about the ruthlessness of managers. Of there being no loyalty in team selection - only form. But in the case of Fellaini, the opposite rings true. This decision smacks of betrayal. Not towards the club. Nor the fans, with the majority unlikely to shed a tear when his departure's confirmed. But to his manager.
It's a battle to name another example of a big time coach constantly going into bat for a maligned player as Mourinho has with Fellaini. From that assuring call before preseason two years go, making it clear he was a valued part of his plans, to his consistent defence of the midfielder - even risking his relationship with the home support. The manager has never wavered. Even having his players rally around their teammate in the face of constant jeers. We all remember the Tottenham saga last season and United's players gesticulating to the Old Trafford crowd to stop barracking one of their own.
And yet now, with the boos silent and Fellaini's place in Mourinho's system established and understood, he's throwing it all away. Or better yet, throwing it all back in his manager's face.
His manager wants him to re-sign. The board does the same. They're in agreement. And like Mourinho, his teammates have also jeopardised their relationship with sections of the support by publicly chastising them for getting on his back. And this is the gratitude he shows?
None of this makes sense. There are scores of players across Europe, far superior in ability to Fellaini, who would crawl over broken glass to be in his position. To see their manager risk it all for them. To have their teammates do the same... and at a club the size of United. Yet he's spurning it all? Why?
It's beyond baffling, even insulting. This is betrayal.
Yes, Fellaini is a great pro. Yes, he does everything his manager asks, without questioning. Yes, the attitude and application can never be doubted. But in the ledger of who has done what for whom, when it comes to Fellaini, Mourinho is well in the black.
As mentioned, last Friday Mourinho conceded he "did not know" if Fellaini would be still with them next season. But over the weekend, things accelerated. Turkey was expected to be his next destination, with twin brother Mansour consistently spotted in Istanbul. High-ranking officials from both Galatasaray and Besiktas confirming contact with his camp over the New Year. But it's now emerged it is Italy's capital where the Belgian is now due to relocate.
The wily Spaniard Monchi, still working his way through a first season in charge of Roma's transfer business, has secured a commitment from Fellaini's minders. Nothing was signed, but Rome sources insist Fellaini "has given his approval" - turning his back on Mourinho and his teammates in the process.
Many amongst the United support will be welcoming the news today, including some ex-players now riding the TV sofa. Fellaini was their anti-hero. The one who epitomised the Moyes and Van Gaal eras.
But Mourinho, from day one, never shared that view. He gave everything for Fellaini to succeed as a Manchester United player. And today's response is nothing short of betrayal.