Slaven Bilic's side were one of last season's surprise packages and their seventh-placed finish earned them a place in the Europa League qualifiers.
But they were knocked out of that by Romanian minnows Astra Giurgiu and have since lost five of their opening six Premier League matches, including the last two in the league at their new London Stadium
Here, we look at five reasons why it is all going wrong for the unhappy Hammers.
1
New stadium
There is a lot of misty-eyed nonsense surrounding West Ham's move from Upton Park to the vast former Olympic Stadium and the so-called lack of atmosphere
In fact, the Boleyn Ground could resemble a library at times, just like any other ground in the country
And, believe it or not, they did lose games there as well
That said, many teams have taken time to adjust to their new surroundings after switching grounds and West Ham are certainly making heavy weather of things.
2
New signings
West Ham brought in 11 new players over the summer and yet only one of them, Andre Ayew, could be considered a starter in Slaven Bilic's first-choice line-up - and he was injured half an hour into his debut
Of the rest, Ashley Fletcher has shown potential but Simone Zaza is struggling to make an impact up front while Gokhan Tore, Sofiane Feghouli and Arthur Masuaku frankly look out of their depth
Their exit from the Europa League has left the Hammers with a bloated squad full of average players.
3
Injuries
New stadium, same old story
Yet while Andy Carroll being injured comes as little surprise, the loss of Ayew and Aaron Cresswell - as well as Dimitri Payet and Manuel Lanzini earlier in the season - has taken its toll
Diafra Sakho's move to West Brom fell through due to concerns over his fitness so he remains at the club, but he too is still injured.
4
Defending
The Hammers have conceded 14 goals in their last four Premier League matches and at times have looked a shambles at the back
Time seems to be catching up with James Collins while Winston Reid and Angelo Ogbonna have become error-prone and Bilic does not seem to trust talented teenager Reece Oxford
All of which makes the sale of James Tomkins to rivals Crystal Palace utterly baffling
Thankfully the experiment of playing Michail Antonio at right-back seems to be over, but on the other flank Masuaku looks like a disaster waiting to happen.
5
Maybe they're not actually that good
Yes, West Ham were challenging for a top-four finish last term, but Leicester won the league, remember? At the end of last season the Hammers lost 4-1 at home to Swansea and slumped 2-1 at Stoke on the final day to drop to seventh
The memorable win over Manchester United in the last game at Upton Park may just have papered over the cracks appearing in a team already on the slide
Payet took the Premier League by storm last season but even he can't win every game on his own
Perhaps teams are finding out that if you keep him quiet, there is not too much else to worry about.
Source : PA
Source: PA