Chelsea's three league defeats this season have all come when Alvaro Morata has played for 35 minutes or lessTEAM NEWS
Chelsea duo David Luiz and Tiemoue Bakayoko are struggling with muscle problems and face fitness tests.
Victor Moses is the latest name on Chelsea's lengthy injury list, he joins the likes of N'Golo Kante and Danny Drinkwater on the sidelines.
Watford have no new injuries so may be unchanged from the win against Arsenal.
Younes Kaboul and Sebastian Prodl remain absent, while Craig Cathcart, Nathaniel Chalobah and Isaac Success are all long-term absentees.
MOTD COMMENTATOR'S NOTES
Guy Mowbray: "The picture has significantly changed since Watford's last visit to Stamford Bridge just five months ago.
"In May, for Chelsea's 'champions homecoming', Watford lost a fifth game in a row with a manager about to be fired. This time, their boss is rightly being feted for guiding Watford to fourth - one place and two points above Chelsea.
"Marco Silva is urging "feet on the ground", but you wouldn't begrudge Hornets supporters being more optimistic than on any of the 10 trips they've made since last winning at the Bridge in 1986.
"Still, Chelsea should win - injuries or not. Anything else could give another slant to Antonio Conte's idea of being in an "emergency situation".
Twitter: @Guymowbray
WHAT THE MANAGERS SAY
Chelsea head coach Antonio Conte on Watford: "I think they are doing very well and they did a really good transfer market. They strengthened very well the squad.
"I am very happy for the Pozzo family (Watford's owners), I know them very well. They have a great knowledge in the football. I am happy for them but we want to beat them."
Watford head coach Marco Silva: "Obviously it's great to look at the table and see what position we are in at the moment. It's too early now, it's not important.
"Everybody knows what our goal is and I haven't changed my words since my first day [here]. We take everything game by game."
LAWRO'S PREDICTION
Watford are having a good time of things at the moment, especially away from home, where they have won three and drawn one of their four games.
Those victories came at Bournemouth, Southampton and Swansea; it is asking a lot for them to go to Stamford Bridge and do the same.
Prediction: 2-0
Lawro's full predictions v England cricket captain Joe Root
Think you can do better than Lawro? Predict the score for this match and the rest of this round's Premier League fixtures in our Predictor game.MATCH FACTS
Head-to-head
Chelsea are unbeaten in 12 league and cup matches against Watford (W9, D3)Watford's only Premier League win in eight meetings with the Blues (D2, L5) was back in September 1999. Alan Smart scored the game's only goal.Watford's last victory at Stamford Bridge was a 5-1 triumph on the final day of the 1985-86 top-flight season.
Chelsea
Chelsea are on a two-game losing streak in the Premier League for just the second time under Antonio Conte.They haven't lost three consecutive league matches since November 2015.The Blues have won one of their four Premier League matches at Stamford Bridge this season (D1, L2).Conte's men have been dropped eight points at home so far this season; two more than in the whole of 2016-17.Chelsea have failed to score in back-to-back home league games for the first time since November 2012.All four of Cesar Azpilicueta's league assists this season have been for Alvaro Morata goals.If selected, Thibaut Courtois will make his 100th Premier League appearance - he has 36 clean sheets to date.
Watford
Watford have claimed 15 points from their opening eight games, which is their best-ever Premier League start.Only under Graham Taylor in 1982-83, in their maiden top-flight season, have they had more points at this stage - on that occasion they had 16.The Hornets have scored in the 90th minute of their last three league games, earning an extra five points.Five of Watford's 13 league goals this season have been scored after the 85th minute. Marco Silva's side have claimed 10 points from a possible 12 away from home.Richarlison has been fouled 27 times this season, an joint-league high along with Dele Alli.SAM's verdictMost probable score: 2-0Probability of draw: 16%Probability of home win: 76%Probability of away win: 8%
SAM (Sports Analytics Machine) is a super-computer created by @ProfIanMcHale at the University of Liverpool that is used to predict the outcome of football matches.
Source: bbc.com