Victory over Benfica came in extra-time on Saturday, which included an almost two-hour suspension of the game on 85 minutes due to a thunderstorm.
Chelsea eventually won 4-1 in Charlotte and Maresca said afterwards: "I am very happy because we are in the last eight teams of this fantastic competition.
"As I say, for 85 minutes, we didn’t concede anything and had enough chances to win the game. The team was very good. It was one of our best performances in the last two weeks or the last month.
"The game was very good for 85 minutes but then we have a two-hour break and it’s not the same game because you break the tempo. Two hours inside. We tried to go out and continue to play in the same way, but it’s difficult.
"It’s not random that for 85 minutes, we didn’t concede anything, and then in five minutes (after the restart) we conceded chances.
"You see they score because they need to chase. We were inside and winning, we go back outside and the mentality is different. It was really difficult."