Manchester City manager Pep Guardiola called his team "lucky" and warned that they cannot take their place in the Champions League quarter-finals for granted ahead of Tuesday's game with Schalke.

City hold a 3-2 lead from the first leg of the last 16 and are expected to progress against a side who sit 14th in the Bundesliga and lost 4-2 to Werder Bremen last Friday.

Despite their impressive domestic success since the Abu Dhabi-backed takeover in 2008, City have yet to progress beyond the semi-final stage in Europe's elite competition and Guardiola has suggested previously that they are not ready to win it, calling them "teenagers" on Monday as well.

Having lost 3-0 to Liverpool in the quarter-final first-leg last season, Guardiola is happy to have a lead over Schlake, but he is determined not to allow for complacency.

"I prefer this scoreline than last time at Anfield when we played at 3-0 down. I prefer this score. We still have a job to do," he said.

"We have a tendency when we see a draw to say who is going to win the second one. One week ago, we didn't expect the results at Paris Saint-Germain or [Real] Madrid would happen. Many things can happen in 90 minutes in this kind of competition.

"I'm sitting here thinking we still have work to do. That is my feeling.

"This competition is judged so that when you go out in the last 16 it's a big disaster. This is a competition that punishes you a lot for your mistakes. We are lucky to be here and 3-2 up."

Guardiola also pointed to United and Ajax's famous comebacks against PSG and Real Madrid respectively last week as proof that City cannot take Schalke for granted.

"If people think Real Madrid going out makes it easy, they don't understand the competition," he said. "I thought they are the favourites because I thought, 'if they can win three, they can win four', but there still remains some incredible clubs. They are of a similar level to Real Madrid.

"Analyse the last one or two months, we are better than [Schalke], but this is one game. It's completely different. Everything is open. That's why we have to be focused. We saw it last week with United, who showed incredible character. Nobody expected it. And a young Ajax team who went to Madrid."