Manchester United hold a six-point lead in the Premiership after Chelsea’s goalless draw against Aston Villa.
He said: “Considering the problems Chelsea have had, Manchester United should be 10, 12, 14 points clear of us. I am happy to be six points behind.
“In my opinion, Manchester United did not take advantage of our bad moments.”
Mourinho added: “Six points is nothing. In previous seasons, we have gone 11, 12 points clear and killed things off by Christmas.
“They (Manchester United) didn’t take their opportunity on Monday when they drew at Newcastle.
“Manchester United have dropped five points at West Ham and Newcastle recently and the gap could have been bigger.
“Now we look forward to the second half of the season when we should have some people back pretty quickly.
“John Terry should be available for the next Premiership game with Wigan and Petr Cech and Arjen Robben for the game after that at Liverpool.”