David de Gea described Manchester United's 4-0 defeat to Brentford as "horrible" and says he was responsible for his side not leaving London with a win.
De Gea allowed Josh Dasilva's tame shot from 25 yards squirm through his grasp to give Brentford the lead, before the goalkeeper's poor pass out to Christian Eriksen led to a second from Mathias Jensen.
Ben Mee and Bryan Mbeumo then ensured Brentford became only the third side to put four past United in the first half of a Premier League game.
It meant United lost four consecutive league matches for the first time since February 1979, while they have also lost seven successive away league games for the first time since losing 10 on the bounce between September and December 1936.
"I cost three points to my team today, to be honest," De Gea told Sky Sports.
"It was a poor performance from myself. After the first mistake and the second, it was very tough for the team to get playing. It was a horrible day.
"We should react better. I should save the first shot and probably the result would be different. It just depends on how the game is going, sometimes I maybe have to read the game better and go long [for the second goal].
"I tried to play when I shouldn't have to Christian. We are not like other teams conceding first and winning 5-1 or 6-1. This is why I cost the team three points
"It was an easy save. We have to react much better and be capable of scoring goals. It was a poor performance. It's easy to play in pre-season when you play for nothing.
"When you play the games that matter, you need bravery and to be proper players. That wasn't the case. We have to keep working, head up, it is the beginning under a new manager and a lot to improve."
United are next back in action a week on Monday when Liverpool visit Old Trafford.