Cristhian Stuani’s early strike gave Middlesbrough the lead but Dale Stephens headed Albion level in the second half, before the Seagulls midfielder was sent off shortly afterwards and Brighton were unable to find the goal they needed to take the second automatic promotion spot from Boro.
Albion now go into the play-offs for the third time in four seasons. They lost to Crystal Palace in the semi-finals in 2012-13 and then to Derby County in 2013-14.
The Seagulls will travel to Sheffield Wednesday in the first leg on Friday and then host the second leg on Monday evening at the Amex. The winners will meet either Hull or Derby in the final at Wembley on May 28.
Whatever happens in the lottery of the play-offs, Seagulls fans will looks back on this season with a great deal of pride.
After a relegation scrap last season, when they finished 20th, Seagulls manager Chris Hughton recruited well in the summer and Brighton started the season with a 21-game unbeaten run. And they have ended the season 14 matches unbeaten after today’s draw.
There have been some sparkling performances in that time and also some which showed real grit and resolve to grind out a result. There is no doubt that with the character and team spirit in the Albion squad, they will be ready and raring to go for Hillsborough on Friday evening
Brighton travelled north in search of a fairytale finish to the season 19 years after Robbie Reinelt’s goal at Hereford prevented them dropping out of the Football League.
In an opening period in which neither side betrayed signs of nerves, Albion striker Sam Baldock saw a first-minute chance deflected out for a corner for the visitors, while Boro’s Albert Adomah just failed to reach a Stuani cross in front of goal.
Brighton had marginally the better of the early exchanges, Stephens seeing a long-range effort tipped over, and Boro keeper Dimi Konstantopoulos plucking an Anthony Knockaert cross off the head of Connor Goldson.
Boro grabbed their opener on 19 minutes, David Nugent flicking on a free-kick and Stuani stretching to poke past David Stockdale in the six-yard box.
Goldson deflected a second Stuani effort over the bar and Ramirez floated an attempted lob onto the roof of the net as Boro pushed to effectively finish the job and rubber-stamp their top-flight return.
Boro ended their first half guilty of squandering a number of good opportunities to score a second, and they were punished nine minutes into the second half when Stephens headed home a Knockaert free-kick at the far post.
But the balance of the game swung dramatically just three minutes later, when goalscorer Stephens was sent off for a foul on Ramirez which left the Uruguayan to be carried off with what looked like a serious injury.
Adomah could have settled the hosts’ mounting nerves when he swung at a loose ball in the Brighton box with three minutes to go, forcing a brilliant point-blank reaction save out of Stockdale.
Boro then saw out the eight minutes of injury-time, before the final whistle blew and the jubilant home fans ran on to the pitch to celebrate promotion.
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