Europa League: Arsenal 3 - 1 Valencia, Gunners fight back from early setback
Diakhaby headed the visitors ahead after only 11 minutes and it could have been two when Guedes nearly capitalised on a mistake from Maitland-Niles.
Lacazette soon turned the game on its head with a quick-fire double, the first a well worked counter-attack and the second a powerful downwards header that Neto will be frustrated not to have kept out.
Valencia threatened in the second half with Cech making a good save from substitute Gameiro but Aubameyany made sure the Gunners will go to Valencia with some breathing space when he volleyed home at the far post late on.