City had to wait until the 88th minute for Raheem Sterling's winner, which ensured that they top their Champions League group with a game to spare.

Guardiola's side had already qualified for the round of 16 following their win in Napoli on Nov. 1 and the Catalan admitted it was hard for his side to maintain their high standard, which has seen them also move eight points clear at the top of the Premier League.

"A win is better than not winning but we are going to analyse the performance," Guardiola told a news conference. "In the first half, we could do better but sometimes, it's difficult.

"When you win a lot of games and you have already qualified, but we had the chance to finish first and we didn't have the right attention to play, but that is normal.

"But we are still winning, we had a fantastic goal from Raheem after an excellent pass from [Ilkay] Gundogan and in the end, we were able to win."

Sterling's strike was his 11th of the season, which is already equal to his best ever tally for a season.

The England international admitted it wasn't an easy night and was delighted to make the difference with his cool finish as he lifted the ball over the on-rushing Brad Jones.

"It's always good to score but the most important thing is to win even if it's ugly sometimes," Sterling said. "Whether it's in the Champions League, the Premier League or Cup games we just want to keep going.

"They kept really solid, we were slow on the ball. They dug in deep and stayed in the game as long as possible. But we're not here just to compete. We want to go as far as we can.

"We have now qualified from the Champions League group stages, playing the game the way that we know can play.

"We are taking it step by step but we are confident that we can challenge the other teams."

Academy youngsters Phil Foden and Brahim Diaz were given an opportunity late on and Guardiola added that the club should be proud that they are producing their own players.

Foden, 17, made his senior debut for the club as a 75th minute substitute for Yaya Toure while Brahim, 18, came on as a substitute in injury time following Sterling's late winner.

The victory ensured City finished top of the group with a 100 percent record and the teenagers could now feature in the final group game at Shakhtar Donetsk.

"A big congratulations to the Academy, the whole club has to be so proud -- young players making their first appearance in a Champions League tournament," Guardiola said.

"If the result had been more clear, they would have got more minutes. They are young talents but our squad is not too big so we will see what happens in the next game.

"Hopefully they can stay for a long time and help to develop the club. I put them on the field but the guys who work with them deserve all the credit."

Despite topping the group, City could potentially face European giants Real Madrid, Bayern Munich or Juventus in the knockout stages.

"We have one game left," Guardiola added. "We are going to see what will happen. It is important now have 15 points. We will see. The draw for last 16 doesn't matter. It always will be complicated."