Heitinga is close to United striker Robin van Persie and was pleased with his part in the win.
"He's very welcome, because Robin is not only a good fellow, but we were at Everton ourselves in an average period and had badly needed this win," said Heitinga to De Telegraaf.
"Now the gap between United and City is 15 points, you have to assume that the title race is run and Manchester United are champions of England.
"That's what Robin deserves. He has earned it with his good season."