The Gunners were facing Sevilla in the Emirates Cup pre-season tournament at the north London stadium.
The home side had conceded first through a Joaquin Correa goal before Lacazette equalised.
But supporters spotted some comical play by Danny Welbeck.
Video shows Alex Oxlade-Chamberlain power past his defender on the right wing.
He looks up and plays a dangerous cross along the ground just in front of the six-yard box.
Welbeck looks set to turn the ball home but instead he somehow completely fluffs his shot.
Luckily his terrible effort confuses the defenders and the ball runs to Lacazette at the far post to stick away.
“Oh dear, Wellbeck…” wrote one viewer.
Another added: “Welbeck's ridiculous miss turned into a swift assist.”
“Danny Welbeck is such a s*** player. Highly overrated,” a third said.
Arsene Wenger’s men won the competition on goal difference despite Sevilla winning both of their games.
They beat RB Leipzig 1-0 but Arsenal thumped Benfica 5-2.
The match saw Sead Kolasinac provide a sublime assist for Theo Walcott.
