Payet was the club's star in what was an excellent final season at the Boleyn Ground, and his stock rose with an excellent campaign with France during this summer's Euro 2016 tournament.
His string of superb performances saw him linked with some of Europe's top clubs, but delighted many by remaining at the Hammers. The Frenchman, however, has only played 45 minutes in the 2-1 defeat to Chelsea. Yet after appearing for France in midweek, Bilic confirmed that he could be involved on Saturday.
He told whufc.com: “We will see how he is but he will definitely be in the squad," and firmly stated "I am expecting him to be fit and ready and he will start the game.”
Bilic continued: “Of course we have missed him. It is the same for any club who are without their key players."
Expecting a tough test
It has been another turn-around at Vicarage Road, with Mazzarri been brought in along with a number of new faces. The Hammers had a 50/50 record against the Hornets last season, with a 2-0 defeat at Vicarage Road, and Bilic is expecting another tough test this time around.
“They are a good team. Last year they did really well and were very active in the transfer market last summer after their promotion," Bilic told his pre-match press conference.
He concluded: “They bought a lot of experienced international players from Europe and now they have changed the manager," and was adamant that “We are expecting a tough game.”
West Ham United will take on Watford at the London Stadium on Saturday, September 10 with kick-off at 3pm BST.