Chelsea must improve next season if they are to defend their Premier League title, says boss Jose Mourinho
The Blues were top of the table from late August and won the title with three games of the season remaining.
However, Mourinho, who has led the club to three league titles, says their rivals will improve next season.
"We have to be better if we want to be successful again. The other opponents are not going to accept this without a fight," he told Chelsea TV.
"Next year will be more difficult, but because it's difficult is one of the reasons why I came back to England. I will enjoy it again."
Despite his warning, the Portuguese told Chelsea fans during an open-top bus parade through west London that they should plan for another victory celebration next season.
"Thank you for everything, for all your support. Book another place for the parade next season. I hope we can give you that," he said.
Second-placed Manchester City and Arsenal, who finished third, are expected to bring in new signings while Manchester United manager Louis van Gaal has been told he can eclipse the £150m he spent last summer.
Departing striker Didier Drogba says Chelsea also need to strengthen to challenge in Europe as well as the Premier League next season.
"The team needs to be stronger next year to compete in the Champions League," he said.
"They are going to buy new players. Also we have young players coming up, the (Dominic) Solankes, (Ruben) Loftus-Cheeks, (Nathan) Akes, all these boys. They need to play."
Drogba also wants goalkeeper Petr Cech, who has one year remaining on his Chelsea contract, to stay at the club.
Cech's future is uncertain after he lost his place to Thibaut Courtois this season after nearly a decade as Chelsea's first-choice keeper.
"No matter what happens I think the club will respect his decision," added Drogba.
"If he wants to stay, he can stay. I think he is more than welcome here. If he wants to go it's his choice as well. It's up to him. But we want him to stay."