Brighton boss Roberto de Zerbi was shocked by their 5-1 home defeat to Everton.
The Seagulls were steamrolled on Monday night at Falmer stadium.
De Zerbi said: "It's very difficult to explain this performance. It was a really strange game. We conceded the first goal after 30 seconds. This wasn't the true Brighton, it's a bad day.
"I think the problem is not about tactical disposition, I think we didn't prepare in terms of motivation, in terms of mentality maybe. Playing a lot of games in a small period is difficult. We are not used to playing so many games in a row. We have to work on this and our mentality.
"I can understand. I'm still proud of my players. The first responsibility is the coach. It's my responsibility.
"We have to remember this game and this date, May 8th, because it can be a very important day for us if we improve in mentality. We have to get ready to play the next game if we want to fight for the big target.
"Before this game we were playing fantastic football, and getting fantastic results. We have to be proud of our work. Today we made a big mistake because we showed we were not ready to play this game. Too many mistakes, we lost the first half, we weren't the true Brighton. This is what we must improve."