Dean Wilkins admitted his Albion side reached a new low after their latest home horror show.
Goals in each half by Doncaster skipper Graeme Lee and livewire striker Danny Cadamarteri means the Seagulls have managed just five wins and suffered nine defeats in 21 matches at Withdean this season.
A lacklustre performance by a revamped line-up left Wilkins angry and puzzled.
He said: "It is probably as disappointed as I have been after a home game this season, because we all knew the importance of putting on a show in our last three home matches and we have not got off to a very good start.
"I am not too sure why we began the game so lethargically.
"It hurts me to say it but we failed to deliver."
As well as the poor results, Albion have now failed to score in six of their last eight home games.
Wilkins said: "That is extremely disappointing. It is difficult for me to say why.
"I feel we owe the fans an apology because they are paying good money to see the team perform and at least provide some goalmouth entertainment.
"We fell well short of that. In the second half we had a lot of possession but that is no good unless you are creating chances."
One bright spot was a promising performance by 19-year old centre half Tommy Elphick. He made his full debut in a team which also contained Doug Loft and Alex Frutos in midfield.
Wilkins added: "It is difficult to judge them because I think they were let down by some of the players around them at times. The one plus was the debut of Tommy.
"I thought he was terrific in a side that did not perform. The quality of our play in possession was so poor at times it looked like they are fearful of playing in front of their own crowd.
"We have to find a solution. That is an absolute necessity because we are letting our public down badly."
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