City lost to a Harry Kane goal deep into added time and saw the nine-point lead over Liverpool at the top reduced to six.
It was the champions’ first league defeat since the loss to Crystal Palace on 30 October last year.
“I said a few weeks ago we need to win many games,” said Pep.
“Every game will be a big, big battle.
“We knew it, and it will be good to understand how difficult it is. Since October we didn’t lose one game in the Premier League.”
The City boss had warned of Tottenham’s threat in his Friday press conference and wasn’t surprised by the level of the visitors’ performance at the Etihad.
“I had the feeling they have fantastic players and a fantastic manager,” Pep added.
“We knew after three defeats they would be back. There was practically no space in the area.
“After that, they could keep the ball and with Kane, it gave time to Son who could run. In general we were there all the time. We were there but we couldn’t win.”
Looking at the goals his side conceded, Pep reflected: “Every goal is different. It was difficult to defend the second one especially when they come from five or 10 yards behind.
“The third one was to the back post and we lost the game.”
