Mario Suarez, Watford's new midfielder, will be playing after joining from Fiorentina at the weekend.
Willain, Chelsea's winger, will be monitored carefully after an opponent stood on his foot in Sunday's game. But, it is not thought to be serious.
What do the managers say?
Quique Sanchez Flores, the Watford manager said to the 'BBC' when asked about Chelsea, "They are playing well, but we are also in the same condition, recuperating good feelings to keep a good position in the league, so I think for sure it will be a very tough match."
Guus Hiddink, the Chelsea manager told the 'BBC' in regards to John Terry, "He is performing and I am convinced he will do regardless of the situation. He will be professional."