Arsenal's players can't say they weren't warned.
"We know the risk, and in football, things can get very equal the moment you are able to match certain things," Arteta said. "That's why our basics and habits have to be through the roof to be able to win the game."
Hours earlier, Arsenal's Under-21 side had beaten a team higher up the English football pyramid than Fleetwood.
Misplaced passes, lost duels, terrible finishing, and a ponderous, weak approach to the occasion. The one bit of fight came from Max Dowman and that was an angry response to a dangerous tackle.
He was shown a straight red card and Arteta aimed some furious words in the teenager's direction as he trudged off, a reaction to suggest Dowman might be waiting some time for his next first-team minutes.
Red card: Max Dowman
PA
There will be talk of this not being a priority competition for Arsenal. That their season will be defined by the Premier League and Champions League.
Forget that. Arsenal made nine changes for this match but the starting lineup was more than good enough to get the job done. It included a World Cup winner, last season's top scorer, and the first-choice striker and right-back.
Instead, Arsenal were sent packing and now they go into a huge Premier League showdown with Liverpool at Anfield this weekend in the worst possible way.
Arteta started both Kai Havertz and Viktor Gyokeres in what was somewhat of a surprise. The expectation was that one of them would be kept fully fresh to face Liverpool.
The reason for that decision was fairly obvious. Gyokeres has not scored this season and Havertz's performance levels have dropped markedly.
Against League Two opposition, Arteta handed his two strikers the chance to rediscover their goalscoring form and gain some confidence for the sterner tests ahead.
The desire to start them both meant Havertz in midfield and Arteta was duly handed another reminder that the German does not belong in that position for Arsenal.
Mikel Arteta was duly handed another reminder that the German does not belong in that position for Arsenal
He missed three big chances and was nowhere close to the required level. It felt almost cruel to keep him on. On this form, you can't start him at Anfield. But what is the alternative? Why would you start Gyokeres?
The Swede scored but it was fortuitous at best. He missed the ball with his right foot, scuffed it with his left back onto his right, and the ball dribbled into the net.
Otherwise, Gyokeres did not look out of place up against League Two defenders. More than once Finley Potter just moved him off the ball. When Gyokeres had the chance to run just before half-time, he went straight out of play.
Arteta has now been left with a selection headache but the worst possible kind. He will not want to start any of those responsible for this showing at Anfield. Mikel Merino might be Arsenal’s best striker right now.
Martin Zubimendi, Piero Hincapie and Cristhian Mosquera were all handed starts after barely featuring in recent weeks but did nothing to suggest more opportunities should be coming their way.
Arsenal were on the wrong side of a major Carabao Cup upset against Fleetwood Town
PA
Ceadach O'Neill was bright on his senior debut and Odegaard made an impact off the bench. The Arsenal captain at least offered the right kind of attitude and intent.
Arteta brought on five players who are likely to start at Anfield. That Odegaard in particular was required to try and mount a rescue act at half-time was bad enough. That it still was not enough for Arsenal to overcome Fleetwood was utterly embarrassing.
More minutes were put into the legs. There was nothing to show for it but humiliation.