The Stamford Bridge outfit currently head Liverpool and Manchester City in the standings, but with their title rivals not featuring in Europe for the remainder of the campaign, Mourinho believes that the Blues are at a disadvantage.
The 51-year-old told reporters: "We play in the Champions League - they don't. We have to play matches with two and three days between. We have to change our focus from Premier League to Champions League and go back to Premier League.
"Liverpool keep going in their perfect season. We have to play Champions League. We have no time to prepare for matches like they have. I think that it's a big advantage they have.
"It is still still open for Arsenal. It is more difficult because they are a few points behind the other teams, but it is still mathematically possible."
Chelsea will attempt to maintain their position at the top of the table when they travel to Crystal Palace on Saturday.