Sir Alex Ferguson believes it would be "foolish" to ignore the threat posed by Manchester City this season.
Ferguson's Manchester United side opened their bid for a record fourth consecutive league title by beating Birmingham 1-0 at Old Trafford on Sunday courtesty of Wayne Rooney's first-half strike. It allowed the Red Devils to keep pace with Arsenal and Chelsea, who both started with victories, along with City, who have been the talk of the summer.
"It would be foolish to ignore developments at Eastlands," said Ferguson. "Manchester City do pose a new threat. We have only to look at how well Chelsea did with back-to-back championships after a massive injection of Russian cash to know money can talk."
He added: "All the leading clubs are looking with interest to see how Mark Hughes handles the situation and whether he can make it work.
"We are all looking over our shoulders, though as far as Manchester United are concerned, it is not in fear."
Indeed, Ferguson feels United will become a more rounded team without Cristiano Ronaldo. The Portuguese world player of the year was certainly missed on Sunday, although only due to the quality of his finishing given United carved out a stack of chances.
Dimitar Berbatov and Michael Owen were both unfortunate not to join Rooney on the scoresheet, with Darren Fletcher also guilty of one poor miss just before the break.
Rooney is the man most Red Devils supporters are looking to fill the gap Ronaldo has left behind. And Ferguson is confident his star striker can contribute at least 20 goals to the United cause.
"If you have two or three strikers who can get you 20 it stands you in good stead." said Ferguson. "Wayne Rooney is well capable of that."