Frank Lampard bemoaned his side’s defensive errors at the London Stadium to hand the Hammers a boost in their fight against relegation.
That was bad news for the Hornets, who are also struggling with back-to-back defeats since a point in their first game back since the restart.
With Manchester United and Wolves closing in on the Blues and Leicester, three points is vital in pursuit of Champions League qualification.
Here is how to watch the game on television or a live stream.
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When is it and what time is kick-off?
The match will begin at 8pm on Saturday 4 July at Stamford Bridge.
How can I watch it online and on TV?
The match will be broadcast live on Sky Sports Premier League, Sky Sports Main Event and Sky Sports Ultra HD.
If you’re not a Sky customer you can grab a NowTV Day Pass here to watch without a subscription.
You can get a live stream through NowTV or the Sky Go app.
Chelsea XI: Kepa; James, Christensen, Zouma, Azpilicueta; Barkley, Kante, Mount; Willian, Giroud, Pulisic
Watford XI: Foster; Femenía, Dawson, Kabasele, Mariappa; Chalobah, Capoue; Hughes, Doucouré, Sarr; Deeney.
Chelsea’s defensive fragility was on full display at the London Stadium and Nigel Pearson will hope to expose that once again. But Frank Lampard’s anger following the defeat against West Ham suggests he should get a reaction here and for all their problems at the back, even with Tammy Abraham struggling, the Blues pose a threat going forward. Christian Pulisic is enjoying his best form since joining the Blues and we expect the hosts to have just enough to maintain the required pace in the battle for a top four finish. 2-1.