Hammers captain Declan Rice made a schoolboy error before kick off and West Ham almost instantly paid the price in first half against Fulham.
With Aleksandar Mitrovic ruled out for Fulham, West Ham were made hot favourites to record back-to-back league wins for the first time in 10 months having beaten Wolves last weekend.
But Fulham have impressed on their return to the Premier League and it was clear to see why as they took an early lead through star player Andreas Pereira.
And unfortunately West Ham had themselves partly to blame.
Declan Rice made a schoolboy error before kick off and West Ham almost instantly paid the price in first half against Fulham.
Hammers skipper Rice had the choice of ends at the London Stadium after the toss before kick off.
One end of the bowl-shaped arena, as West Ham fans know only too well, leaves players and spectators blinded by the sun around this time of day.
By the middle of the second half almost all the pitch will be shaded.
Rice dithered but then decided to stay at the ends the teams were already setup in with Lukasz Fabianski and the West Ham defence facing the first half with the sun in his eyes.
West Ham instantly paid the price when Pereira flashed a hopeful shot from a tight angle on the left side of the box and it flashed through Fabianski like he wasn’t there.
The Pole was criticised by former Hammer Tony Gale on commentary but he also pointed out that the sun was a major factor.
Pereira had absolutely no right to score from there and Fabianski must take his share of the blame.
But for most of the second half Fulham goalkeeper Bernd Leno will not have the same issue.
So Rice will have to put it down to experience as there is no denying the sun being in Fab’s eyes played a big part in the goal.
West Ham are notoriously slow starters anyway, especially after playing in Europe. So a bit more consideration should have been given to the conditions when Rice picked ends.
Craig Dawson came to the rescue by winning a penalty which Jarrod Bowen put away neatly, sending Leno the wrong way.
Gianluca Scamacca has looked lively and been unlucky not to score, forcing two fine saves from the ex Arsenal goalkeeper.
West Ham will need to up their game in the second half to get the win the home support is expecting.