Chelsea manager Jose Mourinho has acknowledged that his side will "have to be better next season" if they are to retain their Premier League title.
The Blues stormed to the top-flight crown this term, seeing off closest challengers Manchester City by eight points.
Mourinho is expecting a far tougher challenge next time around, however, as title rivals City, Manchester United and Arsenal each look to strengthen during the summer.
"It is very difficult to win the Premier League, to win back-to-back," the Portuguese is quoted as saying by BBC Sport. "All the big clubs are not happy, and will try to react.
"We will have to be better next season than this season. If we think that is enough we will be in a difficult situation."
Chelsea take on Thailand All-Stars this weekend as part of their post-season tour of Asia.
