Albion manager Mark McGhee admitted he is very worried after a horror end to the pre-season programme.
The Seagulls were humbled last night by MK Dons, a side relegated from League One last season.
McGhee pulled no punches following a desperate display and he issued a stark warning to his under-performing players ahead of next Saturday's opening fixture at Rotherham.
He said: "It was very worrying, very concerning. It wasn't just a case that the young players who we know are not ready found it difficult, it was also the experienced players who were disappointing.
"We are desperately trying to bring in bodies. I've no doubt that by Saturday we will have two, maybe three players in.
"If players come in, people lose their places in the team, people lose their places on the bench and they end up sitting in the stand.
"If they sit in the stand for too long they will be out of here. People are putting their futures on the line by performances like that."
MK Dons are expected a force in League Two this season under their unconventional new manager Martin Allen and friendly results can be notoriously misleading.
It was, after all, only a few days ago that Albion won at Championship newcomers Colchester but the alarm bells are well and truly ringing now.
According to the MK Dons programme, "a season of steady re-building might not be the worst thing in the world that could happen to Brighton for 2006-07."
Fans will be expecting more than that in League One this season but a clue to the scale of the task facing them was provided by the re-appearance of referee Richard Beeby.
He took charge of the Seagulls in their last match at the equivalent level, the play-off final against Bristol City in Cardiff in May 2004.
Adam Virgo, Danny Cullip and Dan Harding are not around now to hold the defence together and nor are Leon Knight and Chris Iwelumo to score the goals.
There is still time for more signings but the Albion line-up last night was probably not that far removed from the one which will start at Rotherham next Saturday.
The injury-hit centre of defence was occupied by El-Abd and Elphick, with Hart at rightback and Reid at leftback.
Brittain and Frutos were the wide men, Carpenter and Hammond the customary central midfielders, with Kazim-Richards and Robinson in the attack.
Albion began brightly enough on another warm evening at the National Hockey Stadium. Robinson had an angled shot comfortably held by keeper Adolfo Baines, and Kazim-Richards, again demonstrating his eye for the spectacular, fizzed a 25-yarder just wide within the opening 25 minutes.
Henderson had little to do in Albion's goal, apart from a feet-first stop to foil Gary Smith's shot but he was then beaten twice in quick succession. The crossbar came to Henderson's rescue in the 31st minute from a 20-yard freekick by MK Dons' captain Jon-Paul McGovern.
Henderson was left exposed by his back four two minutes later as Dean Lewington lifted a pass over them for Clive Platt to lob over the advancing keeper.
McGhee continued his pre-season policy of giving the goalkeepers a half each, Kuipers replacing Henderson after the break.
Kuipers' first job was to pick the ball out of the back of the net as Lloyd Dyer and Izale McLeod, two of three half-time substitutions by the MK Dons, combined in the 49th minute to double Albion's deficit.
Former West Brom winger Dyer latched onto McLeod's pass and rode Hart's challenge before slotting through Kuipers' legs.
The highly-rated McLeod increased Albion's embarrassment on the hour with a free run on goal and comfortable finish.
Ironically, Albion have this week been tracking Dyer, who is on trial at MK Dons after training with Coventry.
Dyer, aptly named from an Albion perspective, struck his second goal of the game and his team's fourth in the 67th minute with a well-taken free kick from 20 yards.
Kuipers questioned his well-populated wall, the wall questioned his positioning, when in truth credit was due to Dyer for a perfect execution.
At least Albion eventually managed to pierce the MK Dons defence with seven minutes left, Reid making progress into the penalty area to drill a right-footer into the bottom corner
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