It's not the first time Mourinho has taken his frustration out on a water bottle.
Jose Mourinho said he was confident De Gea would stay and commit his future after hailing the Spaniard as the "best goalkeeper in the world" following his stunning save against Young Boys shortly before Fellaini's victor.
But United have triggered the extension clause to keep De Gea at Old Trafford for at least another season and remain in talks with him over a long-term contract.
And no matter how poor the second half display was, to critique the overall performance in such a manner seemed to be purely revved by their agenda to oust Mourinho.
"You need also some other players who are the best in the world".
"I can see Rashford making runs but I can't see a player who's going to pass the ball to him".
"My players were really exhausted at the end and that's what we wanted: it means they gave everything".More news: Chinese consulate in Karachi attacked by gunmen, 3 terrorists, 2 policemen killed
It wasn't just about United's late victor.
Mourinho made the bold decision to leave Paul Pogba and Romelu Lukaku on the bench and Alexis Sanchez out of his squad as his made six changes from a drab goalless draw with Crystal Palace on Saturday.
Reports last month stated that De Gea, with just one Premier League title in eight years, was reluctant to commit his long term future to Old Trafford amid doubts over the side's capacity to compete for major silverware.
But Mourinho defended his record in Europe, saying: 'I play Champions League 14 years, and I qualify 14 times.
"It was relief", said Mourinho.
United's title bid was over nearly as soon as it began this season and he wants to see them challenge for the top honours again like they did under Sir Alex Ferguson. Tepid, because the outgoing players scarcely deserved more and there wasn't enough faith that the incoming players could make much of a difference, despite costing £164 million (Dh768m) between them.
The Frenchman had scored twice in the corresponding fixture in Berne when United won 3-0 and it looked from the opening exchanges, as Rashford chipped over when one-on-one with goalkeeper David von Ballmoos, as if it could be a similarly comfortable night for United.