Lacazette netted Arsenal's first goal of the match four minutes after half-time, through Aaron Ramsey who cushioned the ball backwards to Lacazette, slamming it into the net to make it 2-1.
Antonio Valencia pounced on a Laurent Koscielny mistake to put United ahead after only four minutes, before Jesse Lingard finished a fine move involving Romelu Lukaku and Anthony Martial after forcing Shkodran Mustafi to concede possession.
Jose Mourinho took his team to the Emirates with questions over how they would approach the fixture after a poor recent away record against fellow members of the "Big Six".
Wenger was proud of the attacking endeavour of his players, but was left angry that their efforts were in vain because of a lack of early concentration.
'I trust his feeling and we start with him because he's an important player for us'.
New Everton manager Sam Allardyce watched his side beat Huddersfield 2-0 and Stoke came from behind to beat Swansea 2-1 while West Brom, under new boss Alan Pardew, drew 0-0 against Crystal Palace. Were we too nervous?
"I think there is a desire to go for the grass!"
Paul Pogba clutches his injured hamstring Credit Action Images
Former Premier League champions Leicester City, enjoying a revival under new boss Claude Puel, won 1-0 at home to Burnley courtesy of an early strike from flying winger Demarai Gray. But most of you doing the quiz won't remember football before 1992, so that's why we're sticking with the Premier League era. "But when you go into a big game, you can not make the mistakes that we made".
Paul Pogba will miss the Manchester derby after receiving a straight red card against Arsenal on Saturday. We're certain you'll be able to name at least one, but can you name all three to have achieved the feat?
Mourinho hailed the display as "the best from a goalkeeper in the world".
Lacazette was twice denied by De Gea, who relied on his reactions to keep out a close-range toe poke before needing assistance from the crossbar to keep out another on-target attempt from the Frenchman.
"I don't want to talk about that".
Good luck, and let us know how you do.