West Ham United became the latest team to take a point off Chelsea at Stamford Bridge at the weekend after another lacklustre home performance.

Chelsea have now dropped 14 points at home this season while Liverpool, Manchester United and Arsenal have all stuttered against perceived lesser opposition on their own soil.

Zola, who celebrated an emotional return to Stamford Bridge with a well-earned point, insists better organisation among the lower-profile teams is having an effect on the big four's supremacy.

"I don't think it is only at Chelsea," said Zola. "It seems to me Liverpool, Arsenal and Manchester United are all dropping points and they all play in the Champions League.

"I would also say the smaller teams are getting more organised and playing more tactically. This is making it more difficult for the big teams to beat them.

"This is a very competitive championship and the competition is making everybody else better, including the smaller teams and that is certainly another reason."