Former Chelsea defender Asier Del Horno is confident Valencia can knock Jose Mourinho's men out of the UEFA Champions League.
Chelsea lock horns with Valencia in the quarter-finals on Wednesday with the Spaniards travelling to West London for the first leg.
Del Horno, who quit Chelsea for Valencia, last summer believes the Blues are not as strong as they were because of the new formation they use.
"Chelsea this season are not as well-balanced as they were," Del Horno told The Sun.
"Using the diamond system in midfield and the two in attack does not allow them to play such a flowing game and means they can't impose themselves.
"I believe they have fallen behind Manchester United. They can't hurt us if they don't have the ball and we can't waste the opportunities we get.
"If we get a draw at Stamford Bridge, then we can beat them in the return in the Mestalla.
"The keys to beating Chelsea are we must be very serious defensively, we must not lose concentration or make any defensive mistakes."
The Spanish international insists he bears no grudge against Chelsea for selling him after just one season at Stamford Bridge.
"I bear no grudge or any resentment that they decided to get rid of me. I intend to play well so Chelsea will see the best of me," added Del Horno.
"I hope the Chelsea fans will say 'look at Asier he is a good player.' I also think I was justified in leaving for a team as strong as Valencia.
"Perhaps, because they are not doing so well in the Premiership, Chelsea will be doubly dangerous.
"But when they have been without Terry and Carvalho they have suffered at the back.
"It is good they are the favourites because Inter Milan were when they played us in the last round and we got through that."