Moussa Djenepo made an instant impact off the bench firing Southampton to their first Premier League win of the season.
Within 78 seconds of his introduction, Djenepo cut inside from the left before curling a superb effort past Mat Ryan.
Nathan Redmond added a second goal early in added time, as Saints defeated 10-man Brighton 2-0.
Florin Andone saw straight red on the half-hour mark for a poor challenge on Jan Valery, who was left face down on the Amex Stadium pitch.
But despite going down to 10-men, Brighton remained the most composed of the two and hit the back of the net nearing halftime only for the goal to be called back through VAR.
Lewis Dunk headed home from a corner kick, but Dan Burn had been ruled offside in the build up.
Solly March and Leandro Trossard each went for goal within minutes of the restart, with Brighton pressing for an equaliser.
Djenepo, who replaced Valery on 53 minutes, then produced a stunning right-footed effort from outside of box that lifted Southampton into the lead less than two minutes later.
Nathan Redmond nearly doubled the advantage, but he sent his shot agonisingly wide of the post, which led to a nervy final half-hour for Saints.
Jurgen Locadia would fail to capitalise on a late chance to level the match for Brighton when he smashed the outside of the frame from Glenn Murray’s knockdown header.
Redmond ensured Southampton left as the victories, combining with Sofiane Boufal, whose ball across the goal picked out the winger for a tap in finish.
Brighton: Ryan, Burn, Dunk, Duffy, Montoya, Propper, Stephens (Gross 78), March (Locadia 68), Maupay (Murray 74), Andone, Trossard.
Unused subs: Button (GK), Webster, Bernardo, Mooy.
Bookings: Andone (Red 30).
Southampton: Gunn, Valery (Djenepo 53), Danso, Vestergaard, Bednarek, Ward-Prowse, Romeu, Hojbjerg, Redmond, Ings (Armstrong 84), Adams (Boufal 80).
Unused subs: McCarthy (GK), Cedric, Yoshida, Obafemi.
Goals: Djenepo (55), Redmond (90+1)
Bookings: Ward-Prowse (21), Danso (59), Hojbjerg (82).
Referee: Kevin Friend.