Charlton were forced to settle for a League One play-off place after falling short a bid for automatic promotion despite a 2-0 win at managerless Oldham.
The Addicks were comfortable winners at Boundary Park but results elsewhere stopped them leaping from fifth place to second as Leeds secured the second promotion place.
Phil Parkinson`s side will not meet Swindon for a place at Wembley against the winner of Millwall`s semi-final against Huddersfield.
After a slow start Charlton went in front midway through the first half when Lloyd Sam's deflected cross was tapped in by Nicky Bailey.
Miguel Llera only just failed to connect with a set-piece but the big defender made amends in the 48th minute when he was gifted Charlton's second goal.
Llera hit a tame fee-kick from outside the box yet it somehow squirmed through Darryl Flahavan`s grasp to leave the Oldham keeper red-faced.
Charlton should have gone 3-0 up on the hour mark only for Bailey to fire wide over an open goal after more dreadful Latics defending.
The visitors cruised through to the final whistle, securing their ninth away win of the season as they attempt to bounce straight back up to the Championship at the first attempt.
Oldham, who sacked manager Dave Penney in midweek, posed little threat apart from a Dale Stephens shot which was well saved by Darren Randolph.
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