Former Manchester United star Paul Scholes was not impressed with his side's remarkable comeback victory in the Champions League against Atalanta, warning the Red Devils cannot afford a similar performance against their Premier League rivals.
For the second game in a row in Europe Ole Gunnar Solskjaer's men rallied from a losing position to take all three points late on, winning 3-2 having trailed 2-0 at half time.
Scholes though believes that there is much work to be done, particularly after their display during a tough opening 45 minutes.
What was said?
"I get all the excitement but that first half I just didn't enjoy it and I think that first half put me off the second," the ex-England midfielder told BT Sport. "I think if they were playing a better team they'd be out of sight. That first half was worrying. It looked anything but a team, it lacked unity - that was a worrying sign.
"Can they play Liverpool like that? Never in a million years. Can you play Manchester City like that? Can you play a top Champions League team like that? I don't want to sound like a party pooper but that first half was a major worry for me."
Solskjaer defended his side's display, while admitting he was angry at having conceded twice.
"I thought we played well first half too. Two chances, two goals. It has to stop if we are to survive," he told BT Sport. "We have a habit of doing this at this club. I thought we played well and they scored a goal out of nothing and then another set-piece. But they never stopped believing and kept going.
"Don't disrespect the players. They play for Manchester United and they know they are the luckiest men in the world. Tonight they are the luckiest men in the world because they get to play for Manchester United. That is what so many millions of boys and girls want to do."
The bigger picture
United looked destined for defeat at half-time in Old Trafford after goals from Mario Pasalic and Merih Demiral left them reeling going into the break.
The chances were always there for the hosts and while goalkeeper Juan Musso came up with a string of top-class saves, Marcus Rashford and Harry Maguire both hit in the second half to level the game before Cristiano Ronaldo's towering header wrapped up the win with just nine minutes left on the clock.
Wednesday's triumph leaves United top of Group H, two points clear of Atalanta and Villarreal and with crucial trips to Italy and Spain next up.
They also face a daunting run of fixtures in the Premier League, hosting Liverpool on Saturday before taking on Tottenham and Manchester City.