MONTREAL • Manchester City yesterday confirmed Fulham youngster Patrick Roberts as their third signing of the summer, while Liverpool agreed to sign Aston Villa striker Christian Benteke for £32.5 million (S$69 million).

But even as Chelsea's Premier League rivals continue to splash the cash, Blues manager Jose Mourinho remains unfazed.

After dominating the Premier League from start to finish last term, the Portuguese does not believe that his club need to make major signings to retain their title.

"We are not worried about the others, what they buy, what they have, what they spend - I don't care," he insisted during Chelsea's pre-season tour of North America.

"I don't criticise (the other clubs' spending). I am not against, I understand and accept, I am not afraid... I think it is normal.

"I am happy with the challenge of fighting against these powers."

Chelsea have so far signed squad players in Radamel Falcao and Asmir Begovic - like-for-like replacements following the departures of striker Didier Drogba and goalkeeper Petr Cech.

City, meanwhile, yesterday acquired 18-year-old midfielder Roberts for a fee of £2 million, rising to £8 million with add-ons.

He is the third Englishman to move to the Etihad following an English-record £49 million for Raheem Sterling, and another £8 million for Fabian Delph.

Liverpool and Manchester United have been even busier.

Belgium international Benteke is set to become Brendan Rodgers' sixth major summer signing, following deals for James Milner, Danny Ings, Adam Bogdan, Roberto Firmino and Nathaniel Clyne.

United manager Louis van Gaal is expected to make at least two more signings despite strengthening his squad with the likes of Bastian Schweinsteiger, Memphis Depay, Morgan Schneiderlin and Matteo Darmian for a combined sum of £75 million.

As such, Mourinho has challenged his existing players to improve if Chelsea are to remain the best team in England.

"The fact we are the same is a great challenge for us," he said.

"The only chance to win is if we can be better with the same people.

"The players have to be better individually than last year.

"When they are thinking 'last season I was great', this season that won't be enough.

"John Terry was great last season, this season it won't be enough - (he) must be better.

"Cesc Fabregas is the same.

"The others are going to improve with the players they are bringing in and we have to improve.

"We feel we have the tools to improve our team without that (£60 to £70 million player).

"And the tools are ourselves."

That said, the manager remains keen on signing Everton centre-half John Stones.

Toffees manager Roberto Martinez reacted angrily to news of Chelsea's initial £20 million bid, stressing that the 21 year-old is not for sale.

But Chelsea are reportedly prepared to make an improved offer of £26 million.

"We made a bid, we can make it, it's an open market until Sept 1," said Mourinho, defending the London club's interest in the 21-year-old.

"We didn't make an offer on Sept 2 or in March or two days before we play against Everton.

"We are making the bid in the period we have to make it, which is the open market."

Mourinho did not deny that he would also relish the opportunity to add Juventus midfielder Paul Pogba to his ranks.

However, he suggested that certain targets are out of reach.

"I love the Eiffel Tower but I can't have the Eiffel Tower in my garden," he said. "I can't even have the Eiffel Tower of Las Vegas."

THE GUARDIAN