Antonio Conte's men won the reverse fixture at the King Power Stadium 2-1 back in September but this is a very different Foxes side and they will be confident of causing an upset at Stamford Bridge.
Today, even the 68th minute dismissal of Leicester City's Ben Chilwell couldn't help the Blues gain their first victory of 2018 in a game which remarkably saw Eden Hazard substituted just before the hour mark.
Chelsea's Italian coach will of course be aware that his team need to get back to winning ways quickly, or he may find himself coming under serious pressure.
Chelsea's opponents in the Champions League round of 16 - have already signed Philippe Coutinho from Liverpool for £142 million this month, despite being nine points clear in La Liga; while Manchester City, who lead the Premier League by 15 points, have been linked with a move for Alexis Sánchez, although they face competition from Manchester United.
Leicester wasted four excellent first-half chances and Chelsea only really began to properly compete when Willian and Pedro were brought on with more than 30 minutes remaining.
Conte was quick to defend his main striker after the match, describing the lack of goals as a "problem not only for Morata but for all of the team" and the fact Chelsea failed to conjure a single clear-cut chance pointed to wider issues in their attacking play. "We have great players also and quality in the squad and a great attitude all the time in training sessions on the pitch", said Claude Puel.
"We played Wednesday night and played against a really good team in good physical form like Leicester after only two-and-a-half days. I think in other clubs this doesn't happen".
Watford had trailed until Doucoure got on the end of substitute Troy Deeney's flick on and diverted the ball into the net past Southampton goalkeeper Alex McCarthy, with the ball appearing to come off his arm. I am happy in what I am doing now and what I did in the past.
"I have another year of (my) contract with this club", he said.
"He is learning to deal with these type of situations, and if we speak about Batshuayi we are at the same level. To live this injustice is really hard".
Jonny Evans and Craig Dawson scored to secured a 2-0 win for West Bromwich Albion over Brighton & Hove Albion - their rirst victory in 21 league games.