On a night supporters got their first real glimpse of how Mikel Arteta sees his Arsenal side of the future, the inevitability of their first home defeat of the season shows how much work there is still to be done.
It has been a case of needs must for the Gunners boss since lockdown, with the requirement to tighten things up defensively seeing him shift to the back three system Arteta has used almost exclusively following football’s return in June.
The system is one that served Arsenal well, with the FA Cup secured for a record setting 14th time, but it always felt like one that would soon be abandoned once Arteta believed he had the tools to go with a back four.
The arrival of Thomas Partey from Atletico Madrid on transfer deadline day seems to have been the catalyst for Arsenal’s manager to decide it was finally time to change things up.
The Ghana international - so impressive on his full debut against Rapid Vienna in the Europa League on Thursday night - was handed his first Premier League start against Leicester City as Arteta went with a 4-3-3 at the Emirates Stadium.
It felt like a big moment in Arsenal’s season considering how long Arteta has persisted with a back three, despite all the calls from fans for him to change and go with a more expressive system.
And there were certainly positives Arteta will have taken from the performance, especially in the first half when Arsenal dominated and really should have scored at least once.
But the disappointing second half display that followed will have been a real worry for the former midfielder.
Leicester, who struggled so much before the break, got a foothold in the game and then snatched a 1-0 win when substitute Jamie Vardy came off the bench to grab his customary goal against Arsenal.
The Foxes striker, who famously turned down a move to the Emirates in 2016, has now scored 11 Premier League goals against the Gunners. Only Wayne Rooney (12) has scored more.
With Arsenal having failed to take advantage of their first half dominance - when they had 11 shots on goal - it was not hard to predict what was about to happen when Vardy replaced Dennis Praet with half an hour remaining.
Leicester had ridden the storm and then they pounced 10 minutes from time. One long ball over the top was all it took, with Cengiz Under racing clear before picking out the unmarked Vardy, who headed home from point blank range.
For Brendan Rodgers, it was a moment that capped a perfect game plan. For Arteta, it was a reminder of the work that still needs to be done.
The opening 45 minutes gave an interesting glimpse into the future, with the new 4-3-3 formation allowing Arsenal to play with a freedom fans have not seen from them in a long time.
Partey was at the base of the midfield with Granit Xhaka and Dani Ceballos either side of him, while up front Pierre-Emerick Aubameyang and Bukayo Saka provided the threat either side of central striker Alexandre Lacazette.
Initially it was a system that worked well. The midfield trio dominated the game and David Luiz, sitting just behind them, picked out Kieran Tierney and Hector Bellerin at will.
Arsenal had 11 efforts in 45 minutes, compared to the six they mustered in 90 when they hosted Sheffield United before the international break. They moved the ball well and pinned Leicester back, but they could not make their pressure count.
Lacazette somehow failed to hit the target from inside the six-yard box when picked out by Tierney while Aubameyang headed another good opportunity over, again from a fine Tierney cross.
Bellerin, meanwhile, was denied by Jonny Evans’ excellent block and Saka saw an effort flash into the side netting from a tight angle.
It was all Arsenal, with Leicester mustering just a solitary effort on goal, but the longer the game went on without the home side scoring, the more inevitable the eventual outcome started to become.
Arsenal lost Luiz just after half-time due to injury and there is no doubt the Brazilian’s absence played a major factor in what was an extremely disappointing second-half display.
He had been the man dictating things from deep, but once he went off Arsenal seemed to lose their way.
Bellerin did have one good chance, volleying straight at Schmeichel from Aubameyang’s cross, but that was Arsenal’s only effort on goal in the second 45 minutes.
Leicester started to grow in belief and Vardy’s goal 10 minutes from the end earned them their first win at Arsenal since 1973 and condemned the Gunners to their first home league defeat since they were beaten by Chelsea in December.
The summer additions of Gabriel and Partey have made Arsenal a far stronger unit and give Arteta options he has never had before, but this is a squad that is far from complete.
A worrying lack of goals is a real issue that needs to be solved. Aubameyang has now gone five league matches without a goal for the first time since November 2014, while he was playing for Borussia Dortmund.
Arsenal’s captain has had just eight shots in six league games this season and his expected goals (xG) total of 0.43 ranks only 77th in the Premier League this campaign. It was perhaps no surprise to see him storm down the tunnel immediately after the final whistle.
Arteta needs to find a way of a threat in the final third. The first half was a positive in that regard, but the second 45 minutes showed there was still much more work for his new-look team.