"That was our mistake".
That speculation is unlikely to die down as long as Mourinho, who signed an extended contract until 2020 earlier this year, remains in charge.
Arsenal, which is beginning to find a vein of form under new manager Unai Emery, will take on Brentford Wednesday night, while Liverpool and Chelsea play out a mouthwatering table-topping clash at Anfield the same evening.
Marouane Fellaini headed United's equaliser deep into stoppage-time to make it 2-2, yet even that couldn't dig Mourinho out of trouble. "The minute he gave him a contract extension - which some may say was unnecessary halfway through a season - believing in the manager and showing the faith, he had to then buy him the centre-backs".
Slight risk for severe weather this Tuesday evening
Winds will be a bit breezy out of the southeast between 5 to 15 miles per hour keeping it just a little cooler near Lake Michigan. Temperatures will peak in the mid 70s but that cool front will bring back the 60s later throughout the week.
Reports in the United Kingdom noted that the French midfielder has informed the club's executive vice-chairman Ed Woodward of his plans to join Barcelona after his agent Mino Raiola agreed a deal with Spanish giants after the summer World Cup in Russian Federation. Not exactly what you'd expect from a captain.
The 25-year-old earns 12 million euros net a year and very few teams could afford such wages.
The often-abrasive Mourinho has a history of falling out with high-profile players.
The United manager stopped Pogba in his tracks as he ran on to the training pitch by reputedly asking the player if he was "happy" they lost, before dragging over a club press officer and demanding to know when exactly Pogba posted the clip as a tense, prolonged showdown ensued.
If Lampard was a reminder of better days for Mourinho, the United manager was briefly lifted again thanks to Mata's third minute opener. That's Old Trafford. We are here to attack.
Eight minutes later, Romero was dismissed for handling outside the box and Derby grabbed what they thought was the victor when United's substitute keeper Lee Grant parried a shot from Mason Mount and Jack Marriott nodded in the loose ball.