Pep Guardiola says Manchester City "haven't done anything special" having won just one Champions League.
After winning the Premier League and FA Cup last season, City became just the second English team to complete the Treble when they defeated Inter Milan 1-0 in the Champions League final.
City begin their Champions League title defence when they take on Red Star Belgrade at home on Tuesday.
"It'll be easier. The hardest to win is the first one," Guardiola said.
"For our club to win the Champions League is incredible, but in perspective, how many won one Champions League? A lot.
"We haven't done anything special with just one, but we are incredibly proud."
The City manager said he has not re-watched his side's victory over Inter Milan in Istanbul, where Spain midfielder Rodri scored the only goal.
"I didn't watch the game, not at all," he said.
"I had the feeling they [Inter Milan] were a strong team. They proved it. It was a tight game, but they showed how strong they are and they are a candidate again."
England defender Kyle Walker said City, who are top of the Premier League with five wins from five, will not dwell on last season's Champions League success.
"What we've done is in the past now, it's a new season. The manager drew a diagram and had us at the bottom of the mountain and we have to climb it again," said Walker, who signed a contract extension with City last week.
"Going again is what separates good teams from great teams."
Along with Serbian side Red Star Belgrade, City are joined in Champions League Group G by German club RB Leipzig and Swiss side Young Boys.