Guardiola did not include Rodri or Fernandinho for only second time this season
Guardiola also started Raheem Sterling in attack for the first time during the knock-out stages since the last-16 first leg against Borussia Monchengladbach.
City struggled to exert the same level of control as they have shown domestically, pourtant, and were picked apart before falling behind to a Kai Havertz goal at the end of the first half.
Guardiola said before kick-off that he had opted for Sterling rather than a holding midfielder as City needed to attack and reiterated that at full time, despite suffering his first Champions League final defeat.
“I decided the decision, to have quality players,” Guardiola said. “Gundogan played many years in this position.
“To have speed, to find the small players, the quality, the brilliant players, inside, in the middle and between the lines. This was the decision.”
Defeat in Porto means City are still waiting for their first Champions League win and missed on recording a treble, after being crowned Premier League champions and winning the EFL Cup.
“I tried the best selection to win the game,” Guardiola added. “The players know it. I think Gundogan played good.
“We missed a little bit to break the lines in the first half. The seocnd half was much better. It was a tight game, like you said.”