Jose Mourinho says Chelsea will have to survive a much sterner examination than last season if the champions are to mount a successful defence of the Premier League title.

Mourinho's side begin the new campaign against Swansea on Saturday as the bookmakers' favourites to retain the title they won at a canter, but the Blues boss is convinced the challenge from their rivals will be much stronger this time.

The west Londoners finished eight points clear of second placed Manchester City and rarely looked like surrendering the lead in a title race they led for virtually the entire season.

But Chelsea have spluttered in pre-season and could be without last season's top scorer Diego Costa at Stamford Bridge this weekend due to his recurring hamstring injury.

Those teething troubles, combined with the big spending of Manchester United, Manchester City and Liverpool -- as well as Arsenal's impressive resurgence, have convinced Mourinho that Chelsea will be under severe pressure right from the start this year.

"It depends not just about you, it's also about the others," he said just hours before signing a new four-year contract on Friday.

"You can have a good season and somebody was better than you, a little bit better, a couple of points more than you, then I don't think it's a failure.

"I just think credit to the others. Let's try to be a good team and let's try to be here in March, April speaking to you about the possibility of winning something."

Manchester United open the top-flight season in Saturday's early fixture at home to Tottenham.

They are looking for signs that they are ready to mount a sustained assault on Chelsea's title.

Last season's equivalent fixture, a 3-0 home win on March 15, proved the belated catalyst for a run of form that ensured Louis van Gaal ended his first season as manager with United back in the Champions League places.

But with some £77 million ($120 million, 110 million euros) having been spent on new players including Memphis Depay, Morgan Schneiderlin and Bastian Schweinsteiger, United have set their sights a little higher.

"(Last season) we could see that we were getting better gradually, but we just needed that consistency in our performances and then, obviously, in results," captain Wayne Rooney told ESPN this week.

"But we could see in each game we were getting better. I feel this season for the first time, rather than the last two seasons, we're ready to challenge again."

- Liverpool seek atonement -

Arsenal, bolstered by the arrival from Chelsea of goalkeeper Petr Cech, begin their season with a home fixture against London rivals West Ham United, who now have their former defender Slaven Bilic at the helm.

Manchester City travel to West Bromwich Albion on Monday, while Liverpool, sixth last season, start out at Stoke City, where they were dealt a humiliating 6-1 defeat on the campaign's final day.

"We didn't end the last season particularly well and I think we owe it to the fans to make amends," said Liverpool's German midfielder Emre Can.

"This is why the first few matches are especially important. I think we can start to put (the Stoke result) right with a few good results."

Liverpool manager Brendan Rodgers is expected to hand competitive debuts to a number of new signings, including James Milner, Roberto Firmino and Christian Benteke.

All three promoted clubs are in action on the opening day, with Watford visiting Everton, Norwich City hosting Crystal Palace and Bournemouth tackling Aston Villa in the first top-flight match in their 116-year history.

Having romped to the Championship title, Bournemouth are expected to make a mark in the Premier League, but manager Eddie Howe has warned his players that he will not show them "foolish loyalty".

"I do what's best for the team and if that means being ruthless and making some tough calls, I've proved in the past I'll do that," he said.

Former England manager Steve McClaren begins his Newcastle United tenure at home to Southampton, while Claudio Ranieri starts life as Leicester City manager with a home game against Sunderland.

Fixtures

Saturday (1400 GMT unless otherwise stated):

Bournemouth v Aston Villa, Chelsea v Swansea City (1630 GMT), Everton v Watford, Leicester City v Sunderland, Manchester United v Tottenham Hotspur (1145 GMT), Norwich City v Crystal Palace

Sunday (1230 GMT unless otherwise stated):

Arsenal v West Ham United, Newcastle United v Southampton, Stoke City v Liverpool (1500 GMT)

Monday (1900 GMT):

West Bromwich Albion v Manchester City

AFP