Joe Hart admits Manchester City could be destined for a season of failure unless they come to terms with their new status as a prize scalp for the rest of the Premier League.
Roberto Mancini's side kicked off the new campaign full of confidence after winning the club's first English title for 44 years in dramatic fashion on the final day of last season.
But that optimism is beginning to fade after a disappointing run of just three wins from their first nine games in all competitions.
England international Hart, who underlined his reputation as one of the best goalkeepers in the world with a superb display in Wednesday's 1-1 draw against Borussia Dortmund, believes his team-mates are finding it hard to deal with the increased expectations that come with being Premier League champions and also the extra desire opponents now have to beat them.
They face another test of their mental strength on Saturday as Martin O'Neill's unbeaten Sunderland - the only team to take a home point off City in the league last season - visit Eastlands looking to spring a shock.
It is exactly the sort of fixture that City, who are already four points behind leaders Chelsea, must win if they are to retain the title and Hart said: "I don't know if it is a learning curve, we are in with the big boys now.
"There is no place to hide. There is no point learning if you are not going to win.
"We were pretty open but it allows us to play forward. Hopefully we can shore it up again and be the force that we are."
If City don't win this weekend they are in danger of falling way behind Chelsea, who are heavily favoured to beat struggling Norwich at Stamford Bridge, but Mancini insists he will solve their problems quickly.
"In any league it is more difficult in the second year when you are champions," Mancini said.
"Teams like Fulham, Sunderland and Stoke are better than they were last season and everyone wants to beat us. All we need to do is stay calm and work hard.
"We have three wins and three draws from six games and we should have two or three more points, but it is still a good start and I am sure we will get stronger after the international break."