The Championship play-off contenders took a surprise lead in Tuesday night's Carabao Cup semi-final first leg after Bobby Reid converted past Claudio Bravo from the penalty spot on the brink of half time.
But Guardiola warned how hard it can be against Championship side after drawing with leaders Wolverhampton Wanderers in the fourth round and being held by Huddersfield Town in the FA Cup last season, before their promotion to the Premier League. We win many games in the last minutes because we don't give up.
"It will be tough".
"We've just had the third round of the FA Cup and there is a long way to go in the Premier League and in the Champions League there are lot of contenders as well". "We will take an bad lot from it and learn a lot".
"There's no doubt we're an extreme underdog against Manchester City, so it's very similar to when that Kilmarnock side beat Celtic in the cup final", Johnson told BCFC TV in an interview.
Pep Guardiola's men created numerous chances in a strong response but, after Kevin De Bruyne's well-worked 55th-minute equaliser, they had to wait until substitute Aguero headed in a Bernardo Silva cross in injury time.
Looking ahead to the next game, Guardiola said: "A win helps to win more, then we are there, going to go to London to play the final". Their return could see a more free flowing style of play from the visitors whenever they do get possession of the ball.
City still have it all to do, but Guardiola says they will not be heading to Ashton Gate just defend their lead. I think we have to respect the quality of the opposition, but we showed a good account of ourselves.
Bristol City have lost two games on the bounce in the Championship and have dropped to fourth as a result.
"I'm proud of the football club tonight".
"Now they find themselves in the semi-finals of a major cup competition and facing the best team in the country right now.The concentration levels it will take to ensure we don't get infiltrated in our back-line will be huge".
Guardiola had a brief chat with Lee Johnson after the game, one that the Bristol City manager described as "an interesting conversation... a conversation that I can pass on to the players, and the credit and the kudos that he has given our football team for coming here and trying to play our way". "The one thing I do know is the atmosphere at Ashton Gate with us still in the tie will be phenomenal".