The Portuguese tactician watched his side lose 2-0 to Aston Villa on Sunday after goals from Zat Knight and Gabriel Agbonlahor.

Villa have made several additions to their squad this summer, while the likes of Everton and Manchester City have started well after investing in the transfer window.

"There are a lot of good teams in the league now," said Mourinho. "There is a big improvement in the teams below the top four, so it can be more normal for big teams to lose matches and points this season.

"Other teams have spent money, changed their teams and improved - Villa is just one example, you can find lots of others. It's more difficult now to fight against these teams - but the table after five games does not mean much."

Mourinho gave Villa credit for the way they played, but felt his side deserved a point after dominating for long spells. He was unhappy at the poor defending at a set piece that allowed Knight to score a 47th-minute header from Gareth Barry's corner.

"Aston Villa played well, Chelsea played well and in my opinion a point each would have been a fair result," he said. "But Chelsea made a mistake you cannot make. We are very organised in defence at set pieces. But a game that we were in control of after a solid first half changed with that goal early in the second half. After that, Villa were well organised, showed great spirit and had the crowd behind them.

"The second goal means nothing to me in the context of the game. That can happen sometimes in the last couple of minutes when you are pushing forward. I accept the result but don't think it's fair - but Villa did not make the sort of mistake that we made."