This was another Wenger hokey-cokey of a match. In, out, in, out. And he had to shake it all about. The manager used all three substitutes and abandoned his vaunted three-man defence to rescue this game with his two French strikers in tandem as they eventually overwhelmed Leicester.
What to make of this Arsenal? They have awesome firepower. They have extraordinary depth. And that is even with Alexis Sanchez injured and Mesut Ozil somnambulant.
They were kind of summed up by Granit Xhaka - the midfield enforcer who appeared set on damaging his own side more than the opposition, losing the ball, losing his man, but then delivering a sumptuous flighted pass to pick out another substitute, Aaron Ramsey, who struck the crisp cross-shot that drew Arsenal level and led to the late cavalry charge to victory.
Leicester called foul - pointing out that Ozil handled in the build-up - but Arsenal can counter that, maybe, they should have had a first-half penalty when 2-1 down after Sead Kolasinac attempted to lift the ball over Wilfred Ndidi and it struck the midfielder's outstretched arm.
But Arsenal cannot defend. At times they were thrilling - with Lacazette a fine addition who will score a bucket of goals - but also shocking. Indefensible in their inability to defend.
They were missing Per Mertesacker - confusingly given he was fit despite a nasty cut to the forehead - Laurent Koscielny and Gabriel and Nacho Monreal were tasked with anchoring a three-man defence while alongside him new man, a cult figure in the making, Kolasinac ended up doing Zidane flicks at the end when, really, he should have been finding Row Z rather than trying to be Zizou. But, hey, this is Arsenal.
It was some start for Lacazette. First attack. First goal. The ball was swung out to Hector Bellerin who chested it down to tee up Mohamed Elneny for the cross that was met by Lacazette, stooping to steer his header powerfully beyond Kasper Schmeichel. Just 85 seconds had elapsed. The Emirates erupted. A new hero had arrived? It looked like it especially with the striker's cool-cat celebration. Whisper it but Ian Wright - who Lacazette has been compared to - also scored on his debut. And also against Leicester.
It seemed the visitors would be overwhelmed. But not at all. Leicester hit back with a header of their own and another that probably should have been prevented with Marc Albrighton crossing deep, goalkeeper Petr Cech caught out and Leicester's own debutant Harry Maguire nodding it back across goal for Shinji Okazaki to beat Xhaka.
Less than five minutes had elapsed and there was no let up. This was the first time in the 129-year history of football in this country that the top-flight had kicked off on a Friday (UK time). It was as if people could not wait and it felt like that with the rapid start.
Arsenal threatened but it was Leicester, once more, who were incisive. Again there were mistakes with Xhaka's lazy pass intercepted by Albrighton who sped down the left and crossed for Vardy who swooped to guide the ball home. A trademark Vardy, fox in the box, strike. "We're going to win the league ... again," chanted the gleeful Leicester supporters.
The home discontent, inevitably, began to brew. It was knife-edge football, already, and so it was a relief for Arsenal when Lacazette's shot was smothered but the ball broke to Kolasinac and he calmly passed it back to Danny Welbeck to bundle it home.
What next? Riyad Mahrez, quiet until then, came to life. He forced a corner and took it and from it Vardy was allowed to run free by Xhaka and with Monreal reacting late he glanced his header past Cech.
Now it became frantic. A question of whether Leicester could hold on but when Ramsey struck there was still time, momentum and a wall of pressure from Arsenal. Even so it took a brilliant header from Giroud. The ball cannoned off the bar and over the line before Schmeichel clawed it out. Arsenal, too, were over the line.
