Southampton were on the receiving end of late drama at The New Lawn, as Forest Green Rovers struck an 89th-minute winner in the Leasing.com Trophy.
The young Saints took a first-half lead through Harlem Hale’s cool finish, before Matty Stevens drew the hosts level.
Rovers then took a 71st-minute lead through substitute Dayle Grubb, only for Dan N’Lundulu to strike back as Saints showed their spirit.
But Stevens was in the right place at the right time to secure maximum points for the League Two side with a poacher’s goal at the death.
Radhi Jaïdi’s side made a very promising start, with both Jack Turner and N’Lundulu shooting wide in the first three minutes.
The home team responded in an entertaining opening, as Jack Bycroft was forced to beat away a shot from a tight angle at his near post, before Liam Kitching headed the resulting corner over the bar.
But it was the young Saints who made the breakthrough after 15 minutes, as N’Lundulu capitalised on a defensive mistake and sent his strike partner clean through on goal.
Hale kept his composure to slot the ball under goalkeeper Lewis Thomas to give the visitors the lead.
The game continued in an end-to-end fashion, a very watchable affair, but the Forest Green threat was increasing and the EFL club equalised on the half hour.
After Bycroft denied Stevens with a stunning close-range save, the striker was not to be denied, and moments later headed home at the far post to level the scores.
Rovers ended the half strongly, with Pascal Kpohomouh just doing enough to hold off McCoulsky when winger Junior Mondal delivered a teasing cross, before the latter’s control let him down from a chance of his own.
Saints would have to do some more defending in the second period, as James Morton shot wide from a well-worked corner before Bycroft got down sharply to his left to keep out Kevin Dawson.
The hosts turned the game on its head in the 71st minute, as substitute Grubb found space in the box to shift the ball on to his left foot and shoot low across Bycroft into the far corner.
But Saints showed their spirit to bounce back. First Jake Vokins surged into the box and was so unlucky to see his shot tipped on to the underside of the crossbar by Thomas, before turning the rebound just wide as he threw himself at the loose ball.
Still Saints were not finished, as N’Lundulu led the charge by producing a moment of magic to tie the scores.
All on his own deep in Forest Green territory, the striker slowed down the last defender, then suddenly sidestepped to his left to work a shooting position from which he sent an angled drive in off the far post.
Just as Saints thought they had done enough, Stevens bundled the ball home from close range to snatch victory for the League Two side.
Forest Green Rovers
Lewis Thomas (GK)
Carl Winchester (C)Dan Jones (67′)
Kevin DawsonIsaiah Jones (67′)
Kyle TaylorDayle Grubb (46′)
Jack Bycroft (GK)
Dan N'LunduluDavid Agbontohoma (90′)
Aaron O'Driscoll (C)
Harlem HaleRamello Mitchell (60′)
Jack TurnerKgaogelo Chauke (53′)