Two goals from Mason Greenwood earned Manchester United a narrow victory that again highlighted their old weakness of defending set-pieces.
A 93rd-minute tap-in from substitute Edinson Cavani, from Donny van de Beek’s centre, gave the scoreline a lopsided look and flattered Ole Gunnar Solskjaer's side.
United had taken the lead early in the second half, thanks largely to an outrageous and skilful dummy from Bruno Fernandes, but only managed to hold it for 114 seconds.
And the equaliser once more showcased United’s desperate struggles with set-pieces as Ashley Westwood’s corner found Dean Henderson rooted to his spot and Harry Maguire flat-footed.
James Tarkowski rose and headed in an unstoppable equaliser from inside the six-yard area.
That undid the good work, and impressive opening goal, carved out after 48 minutes when Luke Shaw sent Marcus Rashford sprinting away down the left wing.
His cross was dummied superbly by Fernandes, who allowed the ball through his legs and put the Burnley defence out of the game, for the unmarked Mason Greenwood to sweep the ball in at the far post.
Greenwood’s second, six minutes from time, benefitted from a large slice of luck as he collects a cross-field pass from Paul Pogba and drove into the area from where his shot flew into the Burnley goal via a major deflection off Jack Cork.
Defeat was rough justice on Sean Dyche’s team who made sure new United number one Henderson did not enjoy a day to remember.
Henderson was certainly the most relieved man inside the ground when he conceded after just 16 seconds.
The England keeper made a disastrous failed attempt to punch clear Matt Lowton’s deep cross, allowing Burnley striker Chris Wood to head in, only for the New Zealand international to be ruled offside.
But there was plenty to keep opposite number Bailey Peacock-Farrell busy at the other end.
Greenwood missed their best chance after Fernandes picked out Rashford who drove a low cross through the six-yard box only for his teenage team-mate to slide in and miss connecting.
Peacock-Farrell came to his side’s rescue on a number of occasions, saving well from a Paul Pogba header, tipping over a powerful Rashford shot superbly, and blocking a second-half header from Fernandes.
Henderson 5; Wan-Bissaka 5, Lindelof 6, Maguire 5, Shaw 7; McTominay 6, Fred 5 (Cavani 45, 7); Rashford 7 (van de Beek 83), Fernandes 8, Pogba 7; Greenwood 9. De Gea, Mata, James, Telles, Matic, Williams, Tuanzebe.
Peacock-Farrell 8; Lowton 7, Tarkowski 8, Mee 6, Taylor 6; Gudmudsson 6 (Rodriguez 88), Cork 7, Westwood 7, McNeil 6; Brownhill 6 (Vydra 88); Wood 7. Stephens, Rodriguez, Pieters, Norris, Bardsley, Nartey, Dunne, Richardson.
J Moss 6