Mikel Arteta has made considerable progress in evolving Arsenal since taking charge last December, but Sunday's 1-0 defeat was a slip back into the past as they failed to make their early dominance pay, fizzled out as an attacking force and were undone by a classic counter-attack goal.
"I'm really disappointed, we had it in our hands in the first half," said Arteta to Sky Sports after the match. "They caught us with space at the back and in that moment we lost the game.
"It is difficult to create spaces with 10 men behind the ball, but we should have finished the game better. When it comes to those moments, you can't give away chances at the back.
The villain of the piece from the Gunners' perspective was an all-too-familiar foe: Jamie Vardy came off the bench with 30 minutes remaining, had Leicester's first shot on target all night and scored his 11th Premier League goal against Arsenal to hand the visitors a precious win. Only Wayne Rooney (12) has breached the Gunners more times in League history, and this was an archetypal example of many that have gone before: Leicester moved the ball quickly in midfield, Youri Tielemans spotted substitute Cengiz Under with a raking forward pass and the Turkey international winger teased a ball in from the right wing for Vardy to stoop and head home.
There were, of course, no fans in Emirates Stadium to voice their disapproval, but one small crumb of comfort from their absence will come in the fact they have seen this all before. Vardy could hardly miss, such was the quality of Under's cross, but his clinical touch only heightened the contrast with what happened at the other end for the hosts all night long.
Lacazette was not the only culprit -- Pierre Emerick-Aubameyang headed over from a Kieran Tierney cross, Bukayo Saka was unable to capitalise on several dangerous moments in an otherwise promising display, and Hector Bellerin missed Arsenal's clearest opening in the second half -- but he missed the best chance in the 29th minute when somehow failing to meet another wonderful Tierney delivery with any meaningful contact inside the 6-yard box.
One miss should never define a player, especially one who had a goal disallowed early on for an offside that was theoretically correct, but practically questionable. Granit Xhaka was deemed to be interfering with play as he stood in an offside position, blocking Kasper Schmeichel's view of Lacazette's glancing header from Dani Ceballos' second-minute corner.
For his part, Schmeichel did not protest, punching the ball out of his net in frustration at what he thought was an early concession, yet VAR referee Paul Tierney deemed an interference the goalkeeper seemingly did not see himself.
That said, there was a collective lack of conviction in attack from Arsenal thereafter. Given Saka's fine form and Aubameyang's talismanic status -- even though he's palpably less incisive off the right flank -- Lacazette looks most vulnerable in this team. His lack of aerial ability sometimes compromises Arsenal's effectiveness in the final third. It's a weakness not resolved by Aubameyang or Eddie Nketiah, and can cost them dearly on nights like this.
Lacazette started the season in promising fashion, netting in each of Arsenal's first three games. His understanding with Aubameyang remains a compelling reason to recommend him, as is his pedigree in comparison to the relatively unproven, but promising, Nketiah. Yet it must be difficult for the 29-year-old's mind not to wander a little to what may lie ahead should he start to consistently fall short in front of goal.
No doubt enthused by the chance to champion one of their own, Nketiah has a sizeable section of Arsenal fans calling for the 21-year-old to start more often, and Arteta is clearly a believer, having brought him back from an indifferent loan spell at Leeds last season to reintegrate him into the first-team group ahead of schedule.
There is also the wider picture: Lacazette has entered the final two years of his current contract with no sign of the club opening talks over an extension. It's especially alarming given that how many times Arsenal have been forced into difficult decisions by players with a year remaining on their deals. This is therefore a pivotal season -- one that also ends with a European Championships, and Lacazette hasn't entirely given up hope of forcing his way back into the France setup -- and costly profligacy like this must be the exception.
"Obviously, the strikers need goals. [Lacazette] started tonight, he was sharp and really aggressive in his play," Arteta said. "He had an opportunity to score that goal, and he didn't. But you have to support, give them more confidence and try to create more."
This was Leicester's first away League win at Arsenal since 1973, one that perhaps also benefited from David Luiz and Saka being forced off early with injuries. (Arteta said after the match that Luiz would have a "muscular problem" assessed within the next 48 hours.) Thomas Partey, making his full League debut, looked largely unflustered, but he didn't get close enough to Tielemans for the through-ball that facilitated Leicester's winner, perhaps due to fatigue after playing against Rapid Vienna 72 hours earlier.
Shkodran Mustafi, on for Luiz as a replacement, failed to track Vardy's run despite a visible instruction from Gabriel Magalhaes -- precisely the type of error that will prompt further criticism of the much-maligned centre-back. It might not have mattered, however, had Arsenal translated their earlier superiority to the scoreline.