West Ham boss David Moyes says Brighton deserved their 4-0 win on Saturday.
Goals from Alexis Mac Allister, Jol Veltman, Kaoru Mitoma and Danny Welbeck sent the visitors to a 4-0 defeat, their heaviest of the campaign.
Moyes said: "It was a difficult afternoon.
"We didn't start great, but we knew we were going to have to play a slightly different way and we weren't going to be able to press the ball as much.
"Brighton have got a style and we were going to have to concede quite a bit of possession at times. We did and we conceded a really poor goal to give them the lead from a penalty kick.
"It was a terrible goal to give away and we should have dealt with the ball, the cross-field pass, and we didn't.
"We did get a couple of chances just after [the first goal] Jarrod had a good chance, then Tom cut one back and we couldn't quite get on the end of it.
"We had a couple of opportunities to equalise, but no doubt we were under pressure from the start and Brighton were much better than we were.
"We were still in the game at half-time, so conceding the second from a corner kick so early in the second half was disappointing.
"We conceded the first goal from a corner kick in midweek at Manchester United, and the one we've conceded today is terrible, how the boy can be stood in space to score.
"We work hard on it as you can imagine as we haven't conceded many from corners this season, so conceding the first two goals one from a penalty kick and the other from a corner made all other poor stuff we did look doubly as bad.
"Then after that it was too easy for Brighton to add their third and fourth."