Recent evidence suggests it's time for Arsene Wenger to abandon 3-4-3 formation
Thursday's events at the Emirates Stadium provoked many a searching question. How did legions of Koln fans find their way into the home seats? Was this really a return to football's dark ages or a case of boisterous fun marred by a few individuals? Why could a minority of German fans generate an atmosphere that a majority of Arsenal fans cannot?
But a football match happened too. And it may have proved a consequential one.
In sporting terms at least, the defining moment of the evening came at half-time when Arsene Wenger subbed on Sead Kolasinac for Rob Holding and switched from a back three to a back four. A 1-0 deficit transformed into a 3-1 win; a muddled performance became something rather clearer, and altogether more convincing; suddenly players like Ainsley Maitland-Niles, Per Mertesacker and Hector Bellerin were playing in more natural roles, and reaping the benefits.
Was this the end of 3-4-3? It is an important question to ask, especially heading into a game against Chelsea on Sunday. After all, it is almost exactly a year since the back three which delivered Chelsea to last season's title was born. Sept. 24, 2016 was the date when they travelled to the Emirates and were subjected to an absolute pounding. Down 3-0 at half-time, Antonio Conte changed to a back three and Chelsea never looked back.
At the same time, Arsenal cast admiring glances upwards too. They were not the only club. Southampton, Tottenham and Everton were among the growing number of teams to follow Chelsea's model but it arguably had the most dramatic impact, and implementation, at Arsenal, where Wenger undid 20 years of defensive orthodoxy and finally abandoned a back four in April.
A run of seven defeats in 12 games gave way to a spree of eight wins in 10, culminating most gloriously in the FA Cup final over, yes, Chelsea. So you can fully understand why Arsene Wenger might prove reluctant to change back, especially given the impressive nature of the Wembley win over Sunday's opponents. They also held Chelsea to a 1-1 draw in the Community Shield at the start of this season before winning on penalties, so the formation has a certain charm against Conte.
Still, evidence is mounting that it may prove to be a short-term fix rather than a paradigm shift. More successful than playing Gervinho as a false nine, certainly, though perhaps no more enduring. The win over Koln raised some red flags as a marked improvement came only when a back four was implemented. But that may have been a question of personnel as much as tactics per se: Alex Iwobi and Mohamed Elneny are no one's idea of a commanding central midfield partnership while Holding is chronically short of confidence and Mertesacker didn't exactly look like the reincarnation of Matthias Sammer as he took up positions analogous to those of the old sweepers.
No. The bigger warning signs came in the 4-0 defeat to Liverpool at Anfield before the international break, as a midfield two of Aaron Ramsey and Granit Xhaka were overrun by the home side. Having three centre-backs in theory gives those two central players more freedom to express themselves but to do so, they need the ball, and time on it.
N'Golo Kante is a player built to deny them both of those precious resources and a third midfield presence, Mesut Ozil as a No. 10 perhaps, could be a useful ally on Sunday. Chelsea also play with one central striker, Alvaro Morata, so two centre-backs would still enjoy a numerical advantage even if they lost their third colleague. The conditions seem ripe for a U-turn, especially given Arsenal decided to sell their best performing wing-back, Alex Oxlade-Chamberlain.
Wenger wasn't much interested in discussing the possibility after beating Koln: "I want to use both systems when it suits the team or when we need to do it," he said. "Because we played for a long time in a back four, it is easy for me to switch from a back three to a back four."
Maybe so, but the Koln match showed the value in moving in one particular direction. One match does not a tactical counterrevolution make, but the pre-conditions for change certainly exist.
Maybe it is all academic and Arsenal are destined to lose with whatever formation they put out against Chelsea. It is hardly out of the question. But how Wenger resolves this tactical tension could yet be vital to Arsenal's chances of success this season.
Tom is one of ESPN FC's Arsenal bloggers. You can follow him on Twitter @tomEurosport