Pep Guardiola returns to the Champions League stage with Manchester City claiming his team are not playing well enough to win the competition.

City, who came through a play-off against Steaua Bucharest to qualify, host Borussia Monchengladbach in their opening Group C fixture at the Etihad Stadium.

Guardiola has made an impressive start since taking charge at City in the summer, winning his first six matches and earning widespread praise for some of their play.

Yet that is not good enough for Guardiola, a two-time Champions League winner when in charge of Barcelona, who is demanding improvement from his players.

The Spaniard said: "We have to improve a lot of things.

"Now, after four games in the Premier League, I would like to tell our fans that, (while) we may be first, (with) the way we have played up until now, it will not be enough to win the title.

"Of course, we are so happy for the results, for the numbers and the way we're playing after two months.

"But it is not enough to win the Premier League or achieve the big, big targets in the Champions League."

With tough games ahead against favourites Barca ahead, City will be anxious to get off to a winning start in the group.

But Monchengladbach will provide tough opposition as both City and Guardiola will be well aware.

City faced the German side in the group stage last season and needed late goals to win both games while Guardiola's Bayern Munich took just a point off them in two Bundesliga games last term.

Guardiola said: "It's a brave team, a brave coach and one of the best team of talents in Europe right now. If we let them play, we will suffer. They have a lot of quality.

"The draw was difficult for us - of course Barcelona are there - but especially with Gladbach. I know them, they are a very good team."

Raheem Sterling scored twice in the last 10 minutes when the teams met at Eastlands last December, helping City come from behind to win 4-2 and secure top spot in their group.

That night, which was also Sterling's 21st birthday, was one of the England international's best for City in a generally disappointing first season at the club.

His campaign culminated with a poor showing in England's dismal Euro 2016 campaign but Sterling now seems to have put that behind him with some impressive showings under Guardiola.

He said: "When I was on holiday I simply said I need to come back for the season working hard and showing the manager I'm willing to fight for a place in the team. That's exactly what I plan to do through the season.

"I got a lot of criticism last year which I thought was a bit unfair but I've forgotten about that. It's simply 'play football and don't listen to it'."