Mahrez was moved into the starting XI when Bernardo Silva suffered a problem with his thigh in training ahead of the game, lining up on the right wing as part of a three-man attack.
Guardiola reasoned: "In the second half he was really good. In the first half he was isolated when he had the ball he did not have support in actions two-against-one and one-again-one. When David [Silva] and Sergio [Aguero] moved to the left side there was a problem but he was aggressive and he delivered good crosses.
"We are going to put more people in the box next game - or maybe not, We will see!
"In general, my feeling is the team was so solid. We concede few chances and the team was able to create a lot of chances.
"I know how good they play long balls, second balls when they attack. They are a team who play more with transitions and more with physicality because they are strong, and we played so good.
"Now it is time for rest and recovery and next Wednesday at the Etihad Stadium I invite all of you."