The Belgian playmaker scored his fifth goal in five games and his 13th of the season.
In his 50th Champions League game for City, his goal on 70 minutes proved the difference in the first leg against Atleti.
“He’s in the best moment of the season right now - he is sharp, he’s quick, positive and his influence now again is massive and he made an exceptional goal with his combination with Phil,” said Guardiola.
“It was a difficult game, against tough opponents - they played two banks of 5 for the first 25-30 minutes it was so difficult to find spaces - but we were patient enough except for the first 10.
“The first 5 to 10 minutes of the second half we attacked not at the right rhythm and we didn’t play the way we play.
“But yeah, it was a good result today. We had one or two more chances to score a second with Kevin, but good result and we won the game.
“In games like this we need a striker and they defend so well, so deep and compact and it is difficult to find spaces.
“We were patient because we have to win this type of game and not get anxious and nervous.
“They have incredible talent up front. If you are not attacking in the right way they can punish you."
At his post-match press conference, the City boss was asked what he expected from Atletico Madrid in the second leg next week.
He responded saying that he isn't sure how the Spaniards will play, but that his team need to be ready for everything.
“I don’t know what to expect second leg," said Pep.
"It was different when it was 1-0, we were a little but disorganised and they started to counter-attack and they have incredible quality up front and if you don’t attack in the right way, they will punish you.
“For the second game, I try to expect what I expect of my team.
“I don’t judge what they do are what they are going to do, because I don’t know.
“It is not that I don’t care, it’s more the fact that, OK, we have a game with 1-0 - after we went ahead we were a bit disjointed, the player started to press a little bit higher, they had more combination.
“I guess what happened in the last 15-20 minutes of the game will be how it will be in Madrid.
“We have to prepare and adapt but we have five days prepare to Liverpool and then we go there to try and adapt a little bit better and go there to try and win the game.
“We have to go through our emotions and do what we have to do.
“There will be a referee there. We will prepare tactically and mentally to play in a great stadium with an environment where they have faced this situation many times - more than us. It will be a good test for us on our maturity.”