Albion have slipped to 9th in the Championship after missing out on an otherwise full weekend of fixtures.
With the Seagulls' fixture at Blackburn postponed owing to a waterlogged pitch, they were forced to sit and watch their divisional rivals battle it out from afar.
The gap between Albion and the play-offs remains at 3 points, although Watford now occupy the 6th place position following a 2-0 win over Nottingham Forest - whilst Millwall went down to a surprise 2-1 home defeat to Barnsley.
Derby and Blackpool both lost in front of their home fans, to Hull and Wolves respectively, however Leeds United produced an impressive comeback against high flyers Middlesbrough to seal a 2-1 victory and leapfrog the Albion up into 8th place.
Poyet's men will find themselves with a game in hand after Boxing Day's league match-ups, having already contested that particular fixture (against Millwall) after it was moved forward due to transport issues.