London  - Manchester United begin the defence of their Premier League title this weekend without the man Wayne Rooney calls the best player in the world and with four hungry teams snapping at their heels.

With Cristiano Ronaldo gone to Real Madrid, Liverpool, Chelsea and Arsenal will all be hoping it is their time to shine, while new kids on the block, Manchester City are the latest to see if money can buy success.

If United, who host Birmingham on Sunday, are to win their fourth straight title, they will also have to do it without Argentina forward Carlos Tevez, who has crossed the city divide to join big- spending Manchester City.

Michael Owen and Antonio Valencia have been drafted in to replace Ronaldo and Tevez but Sir Alex Ferguson has yet to spend really big.

"Cristiano is the best player in the world," Rooney said. "If you lose him of course there are going to be questions asked. We might need to play a little bit of a different style to try and keep winning games and trying to win trophies but I am confident we will manage it."

Liverpool, who pushed United closest last year, are chasing their first title since 1989 and have added Glen Johnson and Alberto Aquilani to their squad ahead of their opener at Tottenham Hotspur on Sunday.

Though Rafael Benitez led the side to Champions League victory in 2005, the fact that they have not won the title in so long still hurts.

Though they have lost Xabi Alonso to Real Madrid, in Steven Gerrard and Fernando Torres, they have arguably the best striking partnership in the country and there is growing belief on Merseyside that this could be their year.

"The key for me is not to talk about winning the title but to talk about doing a good job so we can be close, so we can be contenders," Benitez said.

"If we are close I think that we can win the title. We have to fight, we have to do it."

Chelsea begin against Hull City on Saturday, with a new coach in Carlo Ancelotti, who will be itching to show that his side are the true challengers to United's crown.

The Italian has not strengthened his side significantly, but their spine is strong and with Didier Drogba, John Terry and Frank Lampard having committed themselves to the side, they are sure to be contenders.

"The most important thing to win is the Premier League and the Champions League," Ancelotti said. "To win these would be a success, but we also need to have an identity with the team and I think we are going the right way about doing this."

It is four years since Arsenal won a trophy of any kind but Arsene Wenger, as always, is sticking to his guns and believes the current crop of players at his disposal are good enough to compete.

Emmanuel Adebayor may be gone and they have yet to sign anyone of note, but they have Tomas Rosicky and Eduardo back from injury, Andrey Arshavin is playing his first full season and the likes of Jack Wilshere are coming through.

Wilshere has already caught the eye of England manager Fabio Capello and though an injury to Samir Nasri means the Frenchman will miss the start of the season, Wenger believes Arsenal, who take on Everton at Goodison on Saturday, can push for honours.

"I feel we are strong enough, but if we can add then we will do it," Wenger said. "In England, people think that all the problems can be sorted out by buying players.

"The biggest target is to work hard in training, improve what we can improve and have confidence in the players that we have. If we need to add then we will. We have money available so for us it is now important to spend it in the right way when we do it, or if we do it."

The big four may be competing against each other, but they will all have neck ache as they look over their shoulder at Manchester City.

Owner by Dubai billionaire Sheikh Mansour, City have splashed out this summer on Tevez, Adebayor, Gareth Barry, Roque Santa Cruz, adding firepower to an already talented, if erratic side.

"All the expectation will be on us, a hell of a lot of focus," City manager Mark Hughes said. "We had 12 months of it last year and that was when we didn't have players with the ability to get to those expectations.

"We've got a better chance and we have to live up to those expectations now. What I have to do is mould a team that is able to win games successfully and consistently." (dpa)