Sam Allardyce believes expectations are so high at Chelsea that Jose Mourinho will not allow his players to have an off day at Upton Park.
West Ham manager Sam Allardyce expects League Cup winners Chelsea to be at the top of their game when they visit Upton Park on Wednesday.
Jose Mourinho's men are fresh from a 2-0 Wembley win over Tottenham and can take another step towards regaining the Premier League title.
With Allardyce's side having been beaten 3-1 by Crystal Palace last time out, he wants his charges to rediscover the form that saw them come close to winning at White Hart Lane last month.
He said: "We look forward to Chelsea now and it's the third derby in a row. We have to get back to the level of the Tottenham performance to help us try to get a result against the best team in the Premier League at the moment.
"Jose's teams rarely slip up and that's why they're so good. The demand from Chelsea Football Club to the players is that they're not allowed to be off form.
"I expect them to be efficient in every department and that's why they're top of the league.
"They rarely make mistakes and that makes it difficult to score against them.
"For me it's about the players playing their best and hopefully on the day that can help us get the result."
Allardyce confirmed that he has no fresh injury concerns as West Ham go in search of their first win in seven games in all competitions.