United had numerous clear opportunities to score the opening goal in the first half at the London Stadium, but the best chance fell to Dalot who failed to capitalize on an open goal in front of him, missing the target.
Crysencio Summerville went on to give West Ham the lead in the second half before Casemiro headed in United’s equaliser.
United were then left fuming in injury time when Matthijs de Ligt was harshly punished for a minor collision with Danny Ings inside the penalty area.
VAR intervened with Michael Oliver urging referee David Coote to review his on-field decision, which was subsequently changed to a penalty kick.
Jarrod Bowen then stepped up to beat Andre Onana from the spot to seal West Ham’s 2-1 victory.
When asked about Dalot’s miss in his post-match press conference, Ten Hag said: ‘Yeah, but I can also say Alejandro Garnacho twice, Rasmus Hojlund one time, Rashford, Bruno… it’s not fair to pick one of the players out who missed the chances when there were so many missing chances.’
When analysing Dalot’s chance for Premier League productions, Alan Shearer said: ‘We’ll be talking about this in 20 years’ time. The huge, embarrassing misses. Bloopers. Oh my word. He’ll not be wanting to see that again. Absolute sitter. It gets worse every time I see it.’
In a separate interview with MUTV, Ten Hag insisted that United were deserved winners due to the number of chances they created.
‘In football it’s not always the best team winning, today is the perfect example,’ Ten Hag said.
‘Today there was only one team who deserved the win. We played very good football, in and out of possession, dominating the opponent, creating chances.
‘The only thing if you want to win, and that is already a longer issue with us, is that you have to score.
‘The second thing we have to do better is look in the mirror, keep calm, keep focused and head in front of the goal.
‘In the end you lose the game, that’s very frustrating after we made one mistake. We showed again we are a resilient team and the penalty situation where the referee situation has a big impact on the score.’
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