Pep Guardiola had made the decision. The Manchester City manager had known for five or ten minutes and when the half-time whistle blew in Wednesday night’s Champions League match against Inter at the Etihad Stadium, he sprinted to the dressing room, eager to put the plan into action.

It’s a key part of Guardiola’s greatness. The ability to see when and where things are going wrong; to make the necessary changes. Here, not much was going right. City were stuck, unable to find fluidity or sharpness. There was an unusual kind of vulnerability about them.

Inter exuded confidence – except in front of goal. They built calmly from the back. They came on and through City in the transitions. Guardiola was particularly concerned about the moment one of his players lost the ball without support around him.

Inter’s low 5-3-2 block was stifling, yet strangely captivating at the same time, players running en masse from one side to the other, forcing City to recycle quickly, which they were unable to do. Inter’s strikers, Marcus Thuram and Mehdi Taremi, pressed Rodri. City’s midfield pacesetter could not connect the dots.

It was a challenge Guardiola has faced before and will face again – including on Sunday, when City host Arsenal in an early-season Premier League title race. Arsenal parked the bus at the Etihad last season and came away with a 0-0 draw in March, which was very good for a points haul.

Will they adopt a similar approach? It’s easy to think so, especially with their playmaker Martin Ødegaard injured. Mikel Arteta seemed to want his Arsenal team to be tough to beat at Tottenham on Sunday, with solidity the bedrock of their eventual 1-0 win. And if it worked for Spurs, as it did at the Etihad …

There is no doubt that Arteta will examine every inch of Inter’s performance and take ideas from it. Guardiola was asked if the Arsenal match would be similar and he said he didn’t know; it would be up to him to read Arteta’s tactics and react. But he added: “They are an incredible team again, they defend really well, they don’t give away chances, they don’t give away goals, they are really good in many aspects, they control everything.” Which, in summary, sounded like a yes.

Guardiola’s reaction to Inter at half-time shed light on that internal buzz. Kevin De Bruyne was injured in the 44th minute during a confrontation with Inter goalkeeper Yann Sommer, making him a doubt for the game against Arsenal.

But Guardiola would have withdrawn him anyway, taking Bernardo Silva out of the other central attacking midfield role, moving him to the right, while Savinho made way. Guardiola wanted his most agile midfielders in that crowded area, and so Phil Foden and Ilkay Gundogan came in. Rico Lewis was tasked with stepping forward from right-back and cutting inside.

“We needed players in small spaces, who move,” Guardiola said. “Rico, Phil and Gundo are the best we have in that position. In the pocket, the small spaces. The way Inter defended… I thought after 35, 40 minutes that I wanted to make this substitution. After what happened to Kevin and the doctor told me he was not ready to play (on). But I was already thinking about making a substitution at half-time.”

Guardiola was hoping to get Foden into a position to turn and shoot or Gundogan to attack the six-yard box and both scenarios played out, albeit not with the desired outcome. Herein lay perhaps the biggest lesson in terms of the game against Arsenal.

Foden fired straight at Sommer in the 69th minute after a touch from Gundogan in a crowded area; either way and he would have scored. Gundogan then botched two headers in injury time after getting on the end of crosses to make it 0-0. In these types of games, all the tactical nuances and manoeuvres are reduced to a tiny point, the margins are negligible. The point is to be decisive. City can’t be blunt on Sunday.

There is a final, related topic of discussion. Rodri has done much to highlight the issue of player burnout, suggesting that strikes could be an option as the schedule thickens, with two additional Champions League group stage matches under the new format.

Yet Rodri has started just one game this season; so has Gundogan, and Foden has played two 45-minute substitute appearances. Are City’s engine rooms up to such a crucial test? Arsenal will bring with them a near-spotless record from their travels during the calendar year; 11 league games played, 10 wins and a single draw. It was at the Etihad. City will want to do things differently this time around.