The Spanish winger spent six months on loan with Manchester City who have agreed a takeover with the mega-rich Abu Dhabi United Group and signed Brazilian star Robinho for a British record £32.5million.

And Benitez believes the grand designs of City's new investors could make his quest for title success more difficult saying: "You cannot just win the title by spending money but Chelsea won for two years spending big, big money. Afterwards Manchester United won spending lots of money too. If we are talking about spending money then maybe Manchester City will win the title this year."

He added: "It is not just a question of money but if you have more money it is easier. If you don't have too much money, you must do the job as best you can.

"If we are talking now, maybe they (City) need time but if we talk in January maybe they will buy five players...then you never know.

"But it is not just a question of 'I will invest more and I will win'. You cannot guarantee anything."

One consequence of the City takeover Benitez can see taking immediate effect is a hike in transfer fees involving English clubs.

A similar thing happened when Roman Abramovich took over at Chelsea as the billionaire flooded the market with cash - and early talk of a City bid in excess of £120million for Cristiano Ronaldo is unlikely to prevent history repeating itself this time.

"Prices could rise," said Benitez, who is believed to have paid around £8million for Riera.

"That could be a problem. You cannot change these things but you try and get the players you want as cheap as possible, even when prices go higher."