Gary Cahill believes Chelsea will find it difficult to retain the Premier League title next term as their rivals are only going to improve over the summer.

The Blues romped to glory this season, blowing teams away in the first half of the campaign before grinding out results in the closing months.

It means they are once again the favourites to win the title in 2015-16, currently being priced at 2.38 to take the crown, with Manchester City their nearest rivals at 3.75.

Cahill admits it is sure to be a challenge and says Jose Mourinho has already told his players it will be even tougher to defend their crown.

The Portuguese boss guided the club to back-to-back titles during his previous spell in charge and the England international admits his side already know they face a huge test, especially with their rivals all set to strengthen over the summer.

“He’s (Mourinho) told us it will be a lot harder to win it next season, he’s drilling that into us and as players that’s a good thing,” the defender told the club’s official website. “It’s important for us to take his advice as someone who’s been there and done it and no doubt it will be tough because teams always want to beat you when you’re champions, like Man City have found this season.

“You don’t need to be told it’s hard. I know how hard it’s been this season, even though we’ve been at the top all the way through. I’m sure other teams will strengthen in the summer and that will make it even harder for us.”