Chelsea's players begin their Barclays Premier League title defence on Saturday with a stark warning from manager Carlo Ancelotti that they will have to work much harder than last year if they are to hold on to their crown.

Chelsea welcome Roberto Di Matteo's West Brom to Stamford Bridge in Saturday afternoon's late game as they look to build on the league and cup double which the Italian achieved in his first season at the helm.

"It will be more difficult to win the title this year," said Ancelotti.

"It is not enough to be like last year; we will need to work harder. Manchester United will be our biggest rivals.

"They have quality, tradition and history but I know that we have to pay attention to the other teams.

"Arsenal bought a fantastic striker in (Marouane) Chamakh, Liverpool have a new manager, they could be a strong opponent, and we have to look at Manchester City because they bought a lot of good players and they have to build a team. They could be involved in the title race."

The Blues' bid was boosted by the signing on Friday night of Brazil midfielder Ramires from Benfica.

The 23-year-old has joined on a four-year contract having received a work permit and passed a medical. The Blues are thought to have paid £18.2million for the energetic and versatile midfielder.

Ancelotti has predicted a bright future for the 23-year-old, who represented his country at the World Cup.

"He is a fantastic player. He will be the future of the Brazil national team and I hope he will be the future of Chelsea," said Ancelotti.