Thomas Tuchel opted to rest Mount for the visit of Leicester in midweek, with the England international an unused substitute, but is back against he Hornets.
With third-place secured in the Premier League, barring a three-point and 18-goal swing as Tottenham in fourth travel to Norwich, the Chelsea boss has hinted that he may rotate his side and giving some of those on the fringes of the squad a rare opportunity. Saul Niguez gets a farewell outing.
Romelu Lukaku’s poor performance against Leicester sees him dropped. Mateo Kovacic has been unable to recover from an ankle injury, while Andreas Christensen is not included
Antonio Rudiger will be saying his goodbyes to Stamford Bridge ahead of his move away, but Tuchel has kept faith with the German in recent weeks despite that and he should start again.
Ben Chilwell is back in training, after his long absence following surgery on his torn ACL, though Chelsea fans will have to wait until pre-season to see the left-back return to action. Cesar Azpilicueta plays, with Marcos Alonso not in the squad.
Confirmed team news
Chelsea: Mendy, Azpilicueta, Thiago Silva, Rudiger, James, Kante, Saul, Kenedy, Ziyech, Mount, Havertz
Subs: Arrizabalaga, Jorginho, Lukaku, Pulisic, Loftus-Cheek, Chalobah, Barkley, Chilwell, Sarr.
Watford: Bachmann, Femenia, Kabasele, Samir, Kamara, Sissoko, Kayembe, Cleverley, King, Joao Pedro, Sema
Subs: Ngakia, Troost-Ekong, Masina, Cathcart, Gosling, Hernandez, Sierralta, Baah, Elliot.