Jose Fonte got the better of his former club amidst a small chorus of jeers from fans, as Southampton was defeated 3-1 by West Ham.
Manolo Gabbiadini, who arrived on the South Coast for over £14m on deadline day, gave Southampton the lead before West Ham struck three straight times to spoil his debut.
Southampton still has just one win in their last five Premier League outings — the rest defeats — whilst West Ham has collected nine points in that same stretch.
Gabbiadini took advantage of the flag staying down, as he latched onto the end of Jay Rodriguez’s lofted pass before smashing a left-footed effort past the keeper on 12 minutes for his first goal at Southampton.
But West Ham equalised almost immediately when Andy Carroll scooped a shot around a diving Fraser Forster after Pedro Obiang threaded a fine pass between two defenders.
Forster, who was under immense pressure throughout the opening half, had to deny Aaron Cresswell’s volley before preventing Sofiane Feghouli from tapping in on 30 minutes.
Obiang then made it 2-1 with a low, long-range effort, which ran through a cluster of players before finding the bottom corner on the stroke of half time.
Southampton started the second half brightly with James Ward-Prowse drawing two early saves from Darren Randolph, but West Ham punished their opposition’s missed chances.
Mark Noble added a third when his 52nd-minute free kick took a deflection off Steven Davis on its way towards goal and beyond a flat-footed Forster.
Southampton pressed to get back into the game, but Gabbiadini failed to find the target from 12-yards out after the ball broke kindly to his feet on the hour and Ward-Prowse had his header tipped over the bar 10 minutes later.
Southampton: Forster, Bertrand, Stephens, Yoshida, Cedric, Romeu, Davis (c), Ward-Prowse, Boufal (Long 64), Gabbiadini, Rodriguez (Redmond 46).
Unused subs: Taylor (GK), McQueen, Gardos, Clasie, Hojbjerg.
Goals: Gabbiadini (12).
West Ham: Randolph, Kouyate (Collins 71), Fonte, Reid, Cresswell, Feghouli (Calleri 90+1), Obiang, Noble (c), Snodgrass, Antonio, Carroll (Lanzini 56).
Unused subs: Adrian (GK), Fernandes, Quina, Fletcher.
Goals: Carroll (14), Obiang (44), Noble (52).
Bookings: Cresswell (80), Reid (87).