A howler by David De Gea condemned Manchester United to a 1-0 defeat against West Ham at the London Stadium leaving their top-four hopes at risk.

Just a few days ago, United was a strong favourite to finish in the top four of the Premier League. However, they are now in big trouble, while the Hammers are getting closer to safety.

The result depended on a terrible mistake De Gea made in the first half. In the 27th minute, after his team had dominated the first half, he let a harmless shot from Said Benrahma get by him.

De Gea’s mistake happened on the same day that he beat Alex Stepney to become Manchester United’s custodian with the most caps. He played for the 540th time to pass Stepney.

United lost to Brighton on Thursday after giving up a last-second penalty. Earlier in the day, Arsenal’s 2-0 win over third-placed Newcastle gave them a boost.

Even though they still have a game in hand, they are now only one point ahead of red-hot Liverpool in the race to get into next season’s Champions League. They are still in fourth place.

Erik ten Hag was upset, but he stood up for his troubled goalkeeper and said that his team still had a chance to win the league with four games left.

“Mistakes are part of football and in this team you have to deal with it and bounce back because it is a team sport,” the United manager told BT Sport.

“Over the season he is the one with the most clean sheets and also we did it as a team. It can happen, it’s football but everybody has to take responsibility.”

This week, West Ham plays in the semi-finals of the Europa Conference League. They are now seven points ahead of the bottom three teams.

United got off to a good start at the London Stadium. In the 17th minute, top scorer Marcus Rashford hit the outside of the post.

But West Ham took the lead against the run of play when Benrahma’s weak shot from a long way away got by De Gea, who was on the ground.

The Spaniard looked like he had it covered, but his footwork didn’t look right and his hand wasn’t strong enough, even though he got to the ball.

He was lying on the ground, unable to understand what was going on, as West Ham celebrated.

De Gea has had a good and bad season. He is in the lead for the golden glove for most clean sheets in the Premier League, but he has also made some mistakes that have cost his team points.

In the 32nd minute, United hit the post again when Antony’s powerful shot was deflected onto the post and out of play.

This season, Ten Hag’s team has only scored 49 goals, which is the second-lowest total in the top nine. They had 11 shots in the first half, but only one was on target.

As the clock wound down to halftime, De Gea stopped Benrahma’s shot. Victor Lindelof was accused of handball, but referee Peter Bankes didn’t give a penalty.

West Ham put the ball in the goal again early in the second half, but Michail Antonio fouled De Gea, so the referee blew for a foul.

United was in a lot of trouble, and Tomas Soucek headed the ball into the United goal with less than 20 minutes left. However, the officials saved them again by calling the goal back because Soucek was offside.

Ten Hag tried everything, putting on Jadon Sancho and Marcel Sabitzer and replacing Wout Weghorst with Anthony Martial, but they couldn’t find a way back.

David Moyes, the coach of West Ham, praised his team’s “huge character” and said that teams below them would have a hard time catching them, even though they are not mathematically safe.

“The number isn’t confirmed that it keeps you in the Premier League so we have to look forward to the next game and try and pick up more points,” he said.