Mancini was pleased with City's rout of Newcastle United on the weekend.
He said: "The gap isn't the real value. It's seven or six points, not 15.
"That gap isn't correct. We showed this in the first derby when we deserved to win and lost.
"United have the mentality you expect from winning everything in 20 years and you know if you don't play well, it's important to win. But, in the end, every team that wins the title deserves it.
"They won a lot of games to stay on the top and they deserve to win this championship."