City had to come from behind and win a penalty shootout to end a three-year losing streak for the traditional curtain raiser.
Guardiola later beamed: "I enjoyed the season against our rival in Manchester and to start the season with a title is good. We are really pleased.
"We lost a lot of balls, after transitions they are one of the best teams in the world. They are so dangerous to control. But in the end we did it.
"It is nice to play this game because it means you won something in the previous season.
"Now we see how the players come back. The target now is not to win the Premier League, it is 'OK next game try and win it'. This is what we have to do."
On Manuel Akanji, who converted the winning penalty, Guardiola said: "He missed it in the Euros and I love he had the personality to take it.
And on Oscar Bobb's superb performance, he added: "What action.
"He is really good in small spaces and his work ethic, he is really aggressive in the short and long spaces."