Valencia defender Asier Del Horno has criticised Chelsea manager Jose Mourinho in the build-up to the Champions League encounter between the two sides.
Del Horno spent an unhappy time at Stamford Bridge last season before moving to Valencia in the summer, but believes the Blues squad had gone backwards since he left the club.
"Chelsea this season are not as well balanced as they used to be," he 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 and we must not lose concentration or make defensive mistakes."