Dunk, who performed tirelessly at the back for Brighton and produced a brilliant recovery tackle on Lacazette, brought down Sanchez at the end of a menacing run, only for the former Barcelona man to swipe the free-kick over.
Play your top scorer from last season alongside your club record summer signing and you're left with an exciting, effective partnership, right?
This is the first Premier League meeting between Arsenal and Brighton & Hove Albion.
Iwobi began the move with a pass inside to Sanchez.
However, the Gunners did take the lead in the 16th minute when Monreal found the net from around 12 yards out after Brighton had earlier cleared off the line during a scramble inside the box.
But in my experience in big games, perhaps in the past when I was a little bit younger and less experienced, I would think I've got to do something out of the ordinary to match these guys. However, Monreal is a composed footballer and kept his head to shoot home.
Who will get the goals at Brighton?
Blackburn were Wenger's first Premier League victims, back in October 1996. Caught in two minds, the shot lacked the venom needed to beat Ryan. Arsene Wenger's men come into this match on the back of an impressive 4-2 win at BATE Borisov in the Europa League.
The Seagulls found themselves camped behind the ball for most of the half and nearly went behind just over a minute in. It was his first Premier League goal for an incredible 1,660 days.
Alex Iwobi fired in the second in the 56th minute with a shot. "Let's hope that the players come back in a good shape".
Facing a Brighton team lacking impetus without a single striker on the pitch, Arsenal did not have to overexert itself to see off the south-coast side at the Emirates Stadium. After a stuttering start, they managed six exchanges in 25 second-half minutes and were regularly exposing a tiring Brighton backline. We knew it would be a hard game.
Alexis Sanchez was having a good afternoon but it got even better when he produced a sublime assist for Arsenal's second goal.