Pep Guardiola was unflustered at half-time before Manchester City completed their Champions League turnaround against Barcelona, according to two-goal hero Ilkay Gundogan.

The former Borussia Dortmund midfielder converted Raheem Sterling's pass from close range to cancel out Lionel Messi's opener as the interval approached at the Etihad Stadium, despite City being second best for much of initial 45 minutes.

Nevertheless, Guardiola did not see fit to rant and rave as a tactical switch – shifting Kevin De Bruyne in-field and closer to striker Sergio Aguero paid dividends – as the Belgium star drove home a 51st-minute free-kick before Gundogan added his second to crown a 3-1 Group C win.

"He just tells us what he sees from the bench and what we can improve," the 26-year-old explained.

"Sometimes there is a little bit more, sometimes a little bit less. It depends on each game to be honest.

"[Against Barcelona] at half-time, I'm not sure. It was not too much.

"He was not angry, he knew it would be difficult. It's almost impossible to control players like Messi and Neymar for 90 minutes.

"We knew before that we would struggle in part of the game. That happened in the first period. It was important how we reacted and that was right."

Gundogan praised City for being mentally strong in order to overturn the deficit against supreme opponents, who thrashed them 4-0 at Camp Nou a fortnight ago and had won all five of the previous meetings between the sides.

"We changed to a 4-4-2 formation but I'm not sure we should talk about tactics," he said. "It was more about the self-confidence that came back, especially after the goal; about mentality and character.

"It was a good improvement for us and how we reacted after [going behind] and in the first minutes of the second half was really impressive."

Gundogan was part of Jurgen Klopp's fabulous Dortmund side that beat Real Madrid in the 2013 Champions League semi-final before losing to domestic rivals Bayern Munich at Wembley.

Although he accepts this latest triumph over a Clasico giant is not as significant, he hopes City can embark on a similarly memorable journey.

"I think the semi-finals are quite far away at the moment but, you know, in football everything possible," he added. "We didn't expect Borussia Dortmund to get through to the final and beat Real Madrid in the semi-final.

"Everything takes development. In the process we need to wait and hopefully we will go on. Of course we would like to continue like [the Barcelona win], also in the league and in other competitions.

"It was a very special night."