The Red Devils travelled to the London Stadium on Sunday afternoon looking to make it two Premier League wins on the bounce.
Bu the day ended in misery for Erik ten Hag's men, after losing 2-1 in injury time courtesy of a Jarrod Bowen penalty.
And the mood wasn't helped their profligacy in front of goal – typified by full back Dalot's spectacular miss in the earlier stages of the game.
The unfortunate turn of events started just after the game's half-hour mark, when Bruno Fernandes knocked a beautifully weighted ball into the path of Dalot.
Diogo Dalot hit what fans are calling 'the miss of the season' in Man United's loss to West Ham
The Portuguese defender rounded Hammers goalkeeper Lukasz Fabianski, to be faced with a wide-open net.
Instead of slotting the ball home to make it 1-0, his right-footed effort was fired way over the crossbar, to jeers from the home fans.
Fans on social media, meanwhile, were quick to share their exasperation.
Posting on X, one fan quipped: 'It's easier to score than miss from there'.
Another joked it was a covert effort by Dalot to expedite the much-speculated exit of manager Erik ten Hag. They wrote: 'Fans aren't the only ones wanting ETH out by the looks'.
One fan pointed out even chronic miss merchants, including Timo Werner and Darwin Nunez would've done better. 'Even Werner, Jackson, Nunez and Mbappe would've scored this', the fan posted.
Dalot's miss is a reflection of how wasteful United have been in front of goal this season.
They missed out on 22 big chances this Premier League campaign so far, and have failed to score in the first half in eight of the first nine games.