The North West side take on the Magpies at the Sports Direct Arena on Sunday and the blue half of Manchester have the chance to go three points clear at the top of the table before their arch rivals Manchester United play Swansea City later that day.
"Newcastle will be our hardest game - harder than United," said Mancini. "It is strange but it is like this. They have had a fantastic season and are playing to get into the Champions League.
"Their manager is one of the best managers here and it will be a tough game. It is another Champions League final on Sunday. We have two - Newcastle and QPR. We have to keep a big concentration until May 13."