Three quickfire Arsenal goals sank the lacklustre Reds on an afternoon to forget in north London for LVG's side.
The Gunners made a blistering start and found themselves three goals ahead in 20 minutes, a position from which we never recovered and, despite a much improved second half performance, the damage had long been done.
Arsenal started brightly and went close through Santi Cazorla before the hosts went ahead after only five minutes through Alexis Sanchez, who ghosted into space and flicked home at the near post after good work from Aaron Ramsey.
That was a bad start for the Reds, but it got worse a little over a minute later when Mesut Ozil was given the freedom of the Emirates to slam a low effort past David de Gea from close range.
2-0 down in seven minutes, the Reds desperately tried to respond and find a way back, but Arsenal were irresistible, poured forward again and made it 3-0 when Sanchez- unmarked- lashed in the third to all but kill the game as a contest after just 20 minutes.
Shell shocked and reeling by the hosts lightning start, the Reds finally began to threaten and Petr Cech did well to deny Anthony Martial on the turn from point blank range on the stroke of half time.
The second half was better from United- although anything would have been better than the shambolic first- and makeshift left-back Ashley Young forced a good save from Cech.
Martial and captain Wayne Rooney both went close to what would have been a mere consolation, before chances at both ends through Ozil for Arsenal and Mata's curler for the visitors.
Substitute Alex Oxlade-Chamberlain chipped against the bar in the closing minutes as United slipped to third, behind our hosts- who go second- on goal difference.
Credit to Arsenal, they were superb but were given a huge helping hand by the abject Reds in what must surely be the worst performance we've had since LVG took charge.
It's no major crisis-but with Everton next (we all know about our recent record there)- this will act as a wake up call ahead of a two-week break for the international matches.
United Faithful Man of the Match: Anthony Martial
Overall team performance: 3/10