The Hammers are currently 16th in the table, level on points with 17th-placed Watford, with both sides sitting three points ahead of 18th-placed Bournemouth.
As it stands, the Hammers are 16th in the division, three points clear of 18th-placed Bournemouth, meaning that another positive result in this game would leave them in an excellent position when it comes to avoiding the drop.
There is no getting away from the fact that it has been a disappointing season for the club, but a record of two wins and one draw from their last four matches has given their survival hopes a huge boost.
Moyes's side face a trip to top-four chasing Manchester United in their next game on July 22, before finishing their Premier League campaign at home to fellow strugglers Aston Villa on July 26.
West Ham actually have the third-worst home record in the Premier League this season, but Watford have the third-worst record on their travels, which should make for a very interesting game in the capital.
Like the Hammers, Watford have picked up some very important results in recent matches, winning their last two against Norwich and Newcastle United after three straight losses had left them in real trouble.
As mentioned, Watford are currently 17th in the table, with a three-point cushion over Bournemouth, who have an incredibly difficult match away to Manchester City on Wednesday night.
There is no downplaying the importance of this game as a win for either would be huge, but Watford have actually lost their last two Premier League games with West Ham, conceding seven times in the process.
That said, the Hertfordshire outfit recorded a 2-0 victory when they last travelled to the London Stadium in December 2018, where Deeney and Gerard Deulofeu were on the scoresheet.
West Ham Premier League form: LLWDLW
Watford Premier League form: DLLLWW
Having had almost a week to recover from the Norwich clash, it seems likely that Moyes will name an unchanged side for this game, meaning that Mark Noble could again be given an advanced midfield position.
As for Watford, Deeney had to be replaced in the latter stages of their clash with Newcastle due to a knee problem, but the captain is expected to be available for this match.
Tom Cleverley and Roberto Pereyra are two players pushing for a spot in the XI, although Danny Welbeck appears to be in charge of the position on the left, having appeared to have fully overcome his injury problems.
West Ham possible starting lineup:
Fabianski; Fredericks, Diop, Ogbonna, Cresswell; Soucek, Rice; Fornals, Noble, Bowen; Antonio
Watford possible starting lineup:
Foster; Kiko, Kabasele, Dawson, Masina; Capoue, Hughes; Sarr, Doukoure, Welbeck; Deeney
We say: West Ham 1-1 Watford
It is a massive game for both sides, but a draw would, arguably, not be the worst result in the world for either. Both teams are certainly capable of scoring goals, but we are struggling to separate them and are therefore tipping a low-scoring draw at the London Stadium.