Manchester City manager Pep Guardiola says his side must "improve a lot of things" if they want to win the Premier League this season.
City are top of the table with a 100% record after four games, with their most recent victory coming against Manchester United on Saturday.
"The way we have played up until now will not be enough to win the title," said the Spaniard, who succeeded Manuel Pellegrini in the summer.
The Blues last won the title in 2014.
Guardiola, who is preparing his side to face Borussia Monchengladbach in the Champions League on Tuesday, added: "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."
Monchengladbach coach Andre Schubert described his counterpart at City as "the best there is" and said their opponents had a chance of winning titles both at home and in Europe.
"I understand they might be trying to soften expectations but they have incredible strength," he said. "Manchester City has a great chance to win one or two trophies."
Critics were unfair - Sterling
City winger Raheem Sterling has said some of the recent criticism he has faced is unjustified.
The 21-year-old endured a difficult Euro 2016 as England were knocked out in the last 16 by minnows Iceland.
However, he won August's Premier League player of the month after a strong start to the season with City.
"I have had unfair criticism. Last season I made my mark in the Champions League and I equalled my best scoring season," he said.
"Unfair criticism does put you down a little bit. No-one says I am willing to do my best for club and country. At times it is frustrating.
"Pep [Guardiola] has been a massive help. I spoke to him before and he said he watched me at Liverpool. He has made me stronger."
Goalkeepers will make mistakes - Guardiola
Meanwhile, Guardiola has reiterated his support for new goalkeeper Claudio Bravo, who had an eventful debut in Saturday's derby win over Manchester United.
The Chile international was at fault for United's goal and some pundits felt he should have had a penalty awarded against him after a heavy challenge on Wayne Rooney.
Guardiola defended his keeper after the game, saying Bravo had been integral to his side's good first-half performance.
The former Barcelona and Bayern Munich boss said on Monday that all goalkeepers made mistakes.
"I am going to tell you something: goalkeepers will make mistakes," he said. "The opponents will score, I am sure of that."
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