City opened their Champions League group stage campaign with a near flawless 4-0 victory over the Germans to make it seven straight wins in all competitions this season.
Sergio Aguero netted a hat-trick and Kelechi Iheanacho scored late on as City overcame the postponement of Tuesday night's initial scheduling to put Borussia to the sword in front of a smaller crowd of 30,270 at the Etihad Stadium.
"With what these players have done since the beginning - in our games home and away - our players deserve the standing ovation," said a beaming Guardiola at his post-match press conference.
"I'm really happy. I'm so happy. I knew how difficult and important this game was. If we didn't get points in the first game at home against Gladbach, it would make games against Barcelona and Celtic more difficult.
"Today was the most important game in the season. Considering the opponent and the pressure, we played really, really good - the players played at a high level."
City's next Group C Champions League fixture takes place Scottish champions Celtic at Parkhead on September 28 on the same night Barcelona, who beat the Bhoys 7-0, meet Gladbach in Germany.