The Spanish side recently sacked manager Marcelino and controversially replaced him with Albert Celades, who lost his first game in charge 5-2 to Barcelona over the weekend.
But Kepa is expecting a stern test from Los Che at Stamford Bridge.
"Valencia are always going to be a dangerous team," the 24-year-old said at a Cobham press conference this afternoon.
"The circumstances are probably not the best to prepare for a game like this, but at times those circumstances make you show the kind of rage you have inside, and make you a more dangerous proposition.
"I am going to be expecting the best type of Valencia performance. I know the team very well, I know they have some quality players.
"They are a compact team who defend very well. They know how to make the best of their biggest strength, which is their counter-attacking ability, and they have some world-class players."