Substitute Stephen Dobbie scored a 93rd minute winner to break the hearts of Peterborough United, who had defended manfully against a determined Brighton and Hove Albion at the Amex Stadium.
Grant McCann fired wide with the first effort of the evening on eight minutes, but the real opening of the first quarter of an hour arrived for the hosts when Will Buckley tricked his way past Joe Newell and pulled the ball back for Andrew Crofts, but the midfielder fired over from 10-yards.
Mackail-Smith wasted a golden chance to make it 1-0 on 21 minutes when he was afforded a free header from a Bruno cross, but the striker powered his effort straight at Olejnik.
Buckley and McCann both exchanged poor long-range efforts as the game approached the half hour mark. Barnett found the roof of the net with a looping header from a Little diagonal ball as Posh came close to the breakthrough.
Ashley Barnes headed an Orlandi free-kick wide of the target on 42 minutes with the free-kick awarded after Newell had felled Buckley. Newell was booked for the challenge.
Olejnik produced a fine stop to parry a low Barnes effort on 47 minutes before Little curled well wide at the other end after a good Posh counter-attack.
The Posh shot-stopper did well to beat away a fierce drive from Orlandi on 55 minutes as Brighton continued to press. Orlandi then struck the post from distance as Posh rode their luck.
Mackail-Smith squandered a fine chance to break the deadlock following a poor Alcock clearance, the striker tamely shooting wide with his left-foot. Olejnik rather uncomfortably parried a long-range Bridge effort although the former England international did get some swerve on the shot.
Olejnik denied Orlandi on 81 minutes before Mackail-Smith was replaced by Will Hoskins. Gabriel Zakuani replaced Newell on 83 minutes. Barnett tested Kuzcak moments before the end with a low drive, which the goalkeeper saved at his near post.
Deep into stoppage time, the home side got their noses in front as substitute DOBBIE lifted the ball over the advancing Olejnik as a lucky richochet landed at the striker's feet.
Final Score: Brighton 1-0 Posh
Brighton: Kuszcak, Saltor, Greer, Hammond, Dunk, Crofts (sub Dobbie 64min), Barnes, Mackail-Smith (sub Hoskins 82min), Orlandi (sub Lopez 89min), Bridge, Buckley. Unused subs: Ankergren, Calderon, Dicker, Lopez, Lua Lua.
Posh: Olejnik, Newell (sub Zakuani 83min), Brisley, Knight-Percival, Alcock, Little, Boyd, Bostwick, McCann (sub Ferdinand 60min), Barnett, Berahino (sub Tomlin 74min). Unused subs: Day, Anderson, Mendez-Laing, Swanson.
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