Two-goal City lead overturned at Colney
The young Canaries held a comfortable advantage at the break thanks to goals from George Couzens and Kieran Higgs in a promising opening period.
Just 40 seconds into the second half, however, George Tanner fired into the roof of the net to spark a comeback that was completed in the 88th-minute when Angel Gomes netted the winner. Aidan Barlow had earlier drawn the Red Devils level.
"You'd call it the proverbial game of two halves," said Murty after the game. "We were excellent in possession and clinical in the first half, but you can't give a team like Manchester United a leg-up by conceding like that.
"The thing that really disappointed me was the fact that we didn't respond well to it. They got their tails up and got on the front foot, and we didn't have enough players who stood up to the challenge.
"We became a little bit nervous and fractured as a team and we had no real control over the game."
Murty was pleased with his team's efforts in the first half but admitted that they ultimately only served to highlight how far off the expected levels they were after the interval.
He added: "Some of the play was lovely in and around the box. Even some of the stuff that didn't come off was really bright.
"We'd worked all week on controlling the tempo and then changing it in the final third, and I think we saw that today and the goals reflected that.
"I gave them praise at half-time, but I'm just disappointed for the players because the second half was such a contrast. We needed to participate in the game at all times."
FULL-TIME: Norwich City 2-3 Manchester United
NORWICH CITY: Hallett; Syme, Odusina, Owens (Wallis 67), Chatzitheodoridis (Catton 62); Higgs (Aransibia 45), Pollock (c), Sambu, Da Costa; Kamal; Couzens (c). Subs not used: Hale-Brown (GK), Oddy.