Darren Carr has played his last first team match for Albion.
Carr was on the bench again for Rotherham against Notts County on Boxing Day.
He is expected to return to the Seagulls when his month on loan to the Second Division promotion chasers expires next week.
But manager Micky Adams has ruled Carr out of his plans, despite being short of experienced cover in the centre of defence.
"Darren Carr is with Rotherham until after the first of January," said Adams.
"He is not in the equation of playing first team football for Brighton as far as I am concerned."
Andy Crosby deputised alongside Danny Cullip at Barnet on Boxing Day, when Matthew Wicks was sidelined by a hamstring strain. The influential Cullip has been struggling for full fitness of late with a nagging calf problem, but he was back to his best at Underhill.
Crosby, making his first League start since the end of August, performed steadily alongside him, although one second half stumble almost proved costly.
Adams had youngster Adam Virgo on the bench at Barnet as cover for the pair.
It was his first appearance in the squad since appearing in the pre-season friendly at Withdean against Sheffield Wednesday and Adams said: "He wouldn't let us down."
Captain Paul Rogers can also fill in as a central defender in an emergency.
When Adams first came to the club the squad was over-burdened with centre halves, but the likes of Gary Hobson, Ross Johnson and Keith McPherson have all moved on.
The Barnet triumph, achieved in the absence of Bobby Zamora through suspension and Lee Steele through injury, emphasised Adams has options up front.
He can juggle things around to cope with Charlie Oatway's ban from next Saturday's visit by Lincoln.
But don't be surprised if Adams makes a move at some stage, probably in the summer, for Swansea's recently transfer-listed midfielder Martin Thomas.
The Lymington-born hard man was a key member of Adams' promotion winning team at Fulham.
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