Mourinho: Man U still a danger
Chelsea host United and, even though David Moyes' side trail leaders Arsenal by 11 points - and the Blues by nine - Mourinho maintains they can yet retain their crown.
"Arsenal and Manchester City are the top two teams," the Chelsea manager said.
"City have the ammunition and Liverpool have a fantastic chance because they are not in European competition.
"Man United are Man United. Eleven points is a big gap but I believe they'll push all the way.
"We play against the champions. We play Manchester United, not a team 11 points behind the leaders.
"I've played many big matches and this is what my experience tells me. A team that appears to be in the most difficulty can be the most dangerous."
Mourinho is adamant that Moyes needs no words of comfort from him as he looks to make his mark - and silence the naysayers - at Old Trafford.
"There is no reason to have sympathy for Moyes," he said. "He has a fantastic job and is very stable.
"The club gave him fantastic trust, it's a club with a fantastic culture who believe in the manager. He will at least have the time of his contract to build a team and reach success for many years. He has a fantastic job and needs no sympathy."
Mourinho said he is more concerned about creating a lasting legacy at Stamford Bridge than winning the title this season.
"We are not desperate to win the title, I keep saying the same," he said.
"We want to build a team for the future, find a transition between the Chelsea of the last decade and Chelsea of the next decade. But we will try to fight for the title until the end.
"Everyone's going to lose matches I believe. Let's see what is going to happen unless Man City win every game and kill everyone with 20 points difference."
Mourinho said new signing Nemanja Matic will not start on Sunday but he hopes to have Frank Lampard back in his midfield for the first time since the New Year.
"Matic is not starting the game. Branislav Ivanovic I don't think can play. Frank Lampard has a chance as he is training," he said.