The Blues romped to success in 2017/18, winning the title with an unprecedented 100 points - 19 more than second-paced Manchester United.
But this season already looks far more competitive, with just two points separating the top five teams after nine matches.
And ahead of Monday’s game at Tottenham, Guardiola says his players need to fight if they are to become the first team in a decade to retain the Premier League title.
“I don't have doubt about that,” he said. “Two points difference in five, six teams. It’s strong.
“You see line-up for Tottenham. Tottenham are always there.
“They can’t invest because they build an incredible stadium but it’s a top side.
“Last season we did really well in both games, but they are a top team.”
Guardiola believes Tottenham are one of the best teams he has faced since arriving in English football in 2016.
They were the first Premier League team to beat Guardiola’s City – a 2-0 win at White Hart Lane in October 2016 in which they were far superior.
Guardiola believes they are one of the most tactically sophisticated side’s in English football, with Mauricio Pochettino’s ability to switch systems a difficult obstacle to overcome.
“They play with five at back, sometimes diamond, sometimes 4-2-3-1. They can use it and change again.
"When you know a team does the same thing, it’s easier to control it. They sometimes play Son with Dele Alli, they can change it. You have to be prepared for that. Tactically they are very well prepared.
"When we see their game at Inter in Champions League, they were not worse than opponent. I say they were better. But the competition is special. The numbers are the numbers.
"It’s one of the teams I like the most to watch, I learn when I see them.
"They have a young team, good keeper, striker, everything to be there [at the top]."