Manchester City manager Pep Guardiola admitted he was not sure if his team was ready to win the Champions League.
Guardiola led the Premier League champions to the quarterfinals last season, almost matching his best streak at Europe's elite club competition – the semifinals in 2015-16.
The cities are considered among the favorites to challenge again in Europe, but Guardiola said that the clubs with previous successes in the Champions League were great contenders.
"Our great success as a club was the semi-final of the Champions League, throughout our history," he said on Sunday.
"I do not know if we're ready, it's the truth, I do not know, we do not have a lot of history behind us, but a lot of confidence.
" It's not just a matter of coach, players, club and supporters. It is a matter of believing that we can and should win, and honestly, I do not know if we have reached this point.
"There will be a point where [AC] Milan will play again in Europe, and they have won, I do not know, five, six, seven times."
"My favorites are the teams that have a bigger story than us: Real Madrid, Barcelona, these teams.
"I think that Juventus Cristiano [Ronaldo] wanted to show that they want to win this year, they reached the final twice, each time they come close.
" Atlético de Madrid will play at home. It is a team that did very well in recent years. And then there will be another team, and I hope we can be there as well. "
City are second in Group F through two Champions League games this season.