Albion goalkeeper Mark Cartwright has been axed from the team and transfer-listed.
Dutchman Michel Kuipers is back between the posts for tonight's clash against Blackpool at Withdean, which Matthew Wicks misses with a long-term injury.
The double blow for Cartwright follows Saturday's surprise defeat at Cheltenham, when the promotion-chasing Seagulls let in three goals for the first time this season.
Boss Micky Adams said: "We've had a chat about it. I brought Mark into the club, but I don't think he is good enough.
"He is obviously disappointed, but I have to make decisions."
Former Wrexham keeper Cartwright was given a contract for the rest of the season following a loan spell which ended with Albion's 2-0 win at Blackpool in September.
Hernia surgery and Kuipers' form kept the 28-year-old out until Kuipers was dropped for the 1-0 win at Torquay earlier this month because of his poor kicking.
Cartwright went on to claim a club record sixth clean sheet in a row in the League in the last home game against promotion rivals Cardiff.
But Adams was unhappy with his performance at Cheltenham, particularly when Grant McCann beat him with a shot from 30 yards.
Central defender Wicks, injured in the second half, is expected to be out for a month with a torn hamstring.
That means a return to a flat back four, with Danny Cullip partnering Andy Crosby in the middle.
Adams believes individual errors, rather than an unexpected change back to three centre halves, were responsible for the loss at Cheltenham and more places are under threat tonight.
"There will be other changes as well," he revealed.
The players trained yesterday morning and afternoon following Sunday's extra session.
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