Quique Sanchez Flores expects to face a reinvigorated Chelsea when he takes Watford to Stamford Bridge.
The Boxing Day clash will be Guus Hiddink's first game since he returned to the Blues to replace sacked boss Jose Mourinho.
Flores knows the Dutchman well having played under him for three years at Valencia, and expects Chelsea's under-performing players to respond positively.
"It's tougher when a team have changed the manager," said the Hornets boss. "The team know that they need to show for the new manager. But we are ready for the experience.
"They play well and they have lots of experience and quality. We are expecting a very tough match.
"I had Guus for three years as a coach. I have a very good relationship with him, he is a very nice man.
"He's always thinking about the ball, about possession. He's worried about the players feeling free. It was 21 years ago - but things change.
"You analyse three games before (you face a team). But Chelsea are now different to what they were under Jose Mourinho, it is completely different."
Watford travel to west London lying 10 points ahead of the fallen champions in seventh place.
They have won their last four matches, including last weekend's 3-0 victory over Liverpool, to move to within a point of the Champions League places.
Flores added: "We know we are on a good run but the feeling I have in the dressing room is that it's no surprise. We have a strong mentality."
Strikers Odion Ighalo and Troy Deeney have taken most of the plaudits for Watford's fine form, but the defence have also impressed having leaked just 16 goals in 17 games and kept eight clean sheets.
Flores said: "We are always talking about the strikers, and what they do is important, but I'm completely pleased with the defensive line.
"At the start of the season we had problems scoring but the defensive line was working very hard."
Flores also denied any any interest in Roma winger Juan Iturbe, who has been linked with moves to Watford and Bournemouth.
"We decided the names of the players we want, and he is not in our plans," he said.
"We have other names and if we can get them to Watford in January it would be perfect. If not we will continue with the same players."