Southend’s automatic promotion hopes were dented by a late fightback by League Two rivals Stevenage.
The hosts’ Roarie Deacon scored his first career goal when his cross crept into the net, before Joe Pigott levelled with a volley after half-time.
Barry Corr put Southend ahead from the spot but Boro equalised with a penalty of their own from Simon Walton.
Teenage substitute Ben Kennedy curled Stevenage ahead on 86 minutes, then sent Dean Parrett through for a fourth.
Stevenage manager Graham Westley told BBC Three Counties Radio:
“The attitude of the team in the last 25 minutes or so was exactly what you wanted and as an 11 they went forward with real gusto to score three good goals and win the game.
“They’re a decent side and we were in the situation we were in. But we know they do concede late goals and we always fancied we could affect the game late on.
“It’s rude to single out Ben Kennedy for praise. Football’s a team game and when a young kid comes in and does all right, I think it’s rude to ignore the efforts of the team. But it’s great a young kid has come in and done his job very well.
“The pitch was difficult again but people will probably go away saying what a great game, that they can’t wait to get down there again and that’s what you want.”