We approached the second-half much much better.Aitor Karanka
Blues were beaten 3-0 in the third round tie on Sunday afternoon after a trio of first-half goals saw the home side take control of proceedings.
Speaking via Zoom at the Etihad Stadium, the Head Coach addressed the media shortly after his side were knocked out the competition.
And despite coming up against Premier League opposition, Karanka expressed disappointment that his team were unable to challenge the 2018 winners throughout the match.
He said: "We finished the game in the way that we should have started. In the opening minutes, we were brave on the pitch and if Jon Toral had controlled the ball we could have had a chance. But then we started to defend in our box and I knew that if we did this for 90 minutes we would struggle. We weren't aggressive enough.
"The idea was to try and stop them. The main thing is to be aggressive, strong and with a good attitude on the pitch. But if you allow them to play the only thing that will happen is that they score. They are the best players in the world. I knew when I saw their team that Pep respected us and put the strongest team to start the game."
Facing an uphill battle after the break, the 47-year-old went on to praise his team for their character.
Karanka highlighted how his men created genuine goalscoring opportunities and adapted impressively to an unfamiliar formation change during half-time.
The Boss told the press: "We wanted to do something here and in the second-half, we showed we should have the quality to do that.
"We approached the second-half much better and we had a few chances from Jeremie Bela.
"I don't remember when we last played 4-5-1, but playing against Man City we then created chances, we were more aggressive and made the game more difficult for them."
Blues return to action on Saturday when they travel to Middlesbrough for a lunchtime clash with Karanka's former club. The game is available to watch live on Sky Sports Football with kick-off at 12:30pm.