Mourinho believes eighth-placed United and Spurs in ninth will find it difficult to mount a challenge if they slip any further adrift of top spot.
"United are nine points behind Arsenal," he said.
"It is a gap. Tottenham are 10 behind. It is not a gap for us because we are speaking about five or six points, that is not a gap. It is something that in two matches can be over, but nine or 10 points is a gap.
"I keep saying that there is a lot of games to play in December and at the beginning of January we can have a look and see if all six are within shorter distances.
"Spurs and United know that if the next step is to reduce from 10 to seven or from nine to six it is to get them back in to the race, but they know that if the next move is from 10 to 13 it becomes hard.
"Arsenal are much more comfortable because they can slide in one match and nothing matters to them but some teams know the next slide could be crucial.
"The six teams are very equal in their potential. I see the six teams as very good teams and there are other teams doing very well. Everton and Newcastle are doing very well."
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