It is less than four months since City overcame United in the semi final of the FA Cup after which City went on to end a 35 year drought without a trophy by beating an off form Stoke side.
But Phelan says it makes no difference that it is City.
"It is no different," said Phelan.
"It is a tasty one of course because it is the two Manchester clubs coming up against each other.
"But we may try out a few new things. We have a week to prepare.
"The FA Cup semi-final was disappointing. But this is a new season.
"We will have a look at a few new players to see if they can handle it and take us into the league. That is what it is all about.
"Manchester United is all about challenges. You get them every day. Next Sunday will be no different."