Britt Assombalonga's late goal enabled Southend to overcome Wycombe for their first league win in four games.
Dean Morgan had given the hosts the lead against his former club, coolly finishing off Matt McClure's delivery.
But the Shrimpers pulled level thanks to Barry Corr, who tapped home following Kevan Hurst's corner.
And Assombalonga's fine solo effort five minutes from time completed the comeback to earn the Johnstone's Paint Trophy finalists three points.
Defeat for the Chairboys was their third in a row, while Southend's win left them just two points outside the play-off places.
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Southend United manager Paul Sturrock told BBC Essex:
"It was a stodgy first half - the excitement of Wednesday night (ensuring a trip to Wembley in the Johnstone's Paint Trophy), looked as if it was going to take its toll.
"But the boys rolled their sleeves up the second half and stuck to the game-plan. We started to dominate and we could have went on and scored a few more.
"It wasn't a calf injury (for Chris Barker), it was an Achilles, we don't know how bad it is. There are a couple of players that got knocks. Reeves pulled something and Leonard felt his hamstring again.
"That would be a blow because Leonard's second-half performance was strong, he did all the right things."