Thomas Tuchel's Chelsea side picked up a crucial away win against Claudio Ranieri's Watford with a 2-1 victory at Vicarage Road.
The first half saw Mason Mount give the Blues the lead. However, before half time, Emmanuel Dennis levelled for the hosts.
In the end, a Hakim Ziyech goal was enough to give Chelsea all three points in what was a disappointing display from Tuchel's men.
Here's five things we learned from Chelsea's win against Watford:
1) The absence of N'Golo Kante and Jorginho was evident tonight
Going into the showdown with Watford, The Blues were without N'Golo Kante and Mateo Kovacic. On top of that, Jorginho had a late fitness test and wasn't fit enough to start. Therefore, Tuchel opted to start both Saul and Ruben Loftus-Cheek in midfield. Right from the get-go, the pair struggled. There was no clear organisation, and it was too easy for Watford to break through Chelsea's midfield. Going forward, it is vital that the Blues have both Kante and Jorginho fit. It's refreshing to have so many options all over the pitch, but Ruben and Saul have not impressed in recent weeks. Since the arrival of the Spaniard, Saul has really struggled to settle in the Premier League. It's fair to say that Chelsea are unlikely to keep the midfielder on a permanent basis.
2) Reece James and Ben Chilwell are pivotal to the team
With Ben Chilwell out until January at the earliest, it was vital that the Blues kept Reece James fit. Unfortunately, the wingback failed a late fitness test and was unable to feature against Watford. Both James and Chilwell have impressed the masses this season. James has taken his game to the next level. Chelsea look slightly lost when James is not on the pitch. Against Watford, Cesar Azpilicueta and Marcos Alonso both started at wingback. From the first whistle, the pair looked uncomfortable and were sloppy when it came to defending. If Chelsea are to compete on all fronts, it is crucial that both James and Chilwell are in the side.
3) The Blues cannot afford to play like this going forward
In the first half, Ranieri's men came out guns blazing from the off. Watford were sharp and efficient in their pressing and caused Chelsea a lot of issues. Tuchel's midfield were out of shape and it seemed as if there were a lot of holes in the Blues' game. Despite picking it up slightly in the second half, Chelsea still showed holes in the game in what was an unconvincing display from the team.
4) The importance of having everyone fit
Going into the clash with Watford, the Blues were without several key men. The likes of Timo Werner, Reece James, Ben Chilwell, N'Golo Kante and Mateo Kovacic were unable to feature. Throughout the season so far, Chelsea have had to deal with a lot of injuries in their side. Tuchel has aspirations of winning the title this season. However, if he wants to mount a successful title charge, it is vital that he has a fully fit squad to choose from. Otherwise, the likes of City and Liverpool will catch up with the Blues.
5) Edouard Mendy continues to prove why he is the best in the business
Throughout the season so far, Edouard Mendy has got Chelsea out of a lot of issues. His presence in the net is reassuring for the Blues faithful. In the game against Watford, Mendy had to perform some heroics to give Chelsea all three points. On any other day, without Mendy, the Blues would have looked at another two points dropped. Chelsea re really going to miss Mendy when he flies off to the African Cup of Nations in January.