Southampton came crashing back down to earth after suffering their first defeat in six Premier League games, which could prove costly in the race to beat relegation.
Cardiff City’s Kenneth Zohore scored deep into stoppage time after Southampton had levelled in the 91st-minute in a 2-1 defeat at St Mary’s.
Jack Stephens appeared set to rescue a crucial point for Southampton against fellow a relegation candidate, but Zohore instead lifted Cardiff above their opponent and up to 15th in the table.
Southampton sits just outside of the bottom three, but would slip below the line if Burnley pick up a point in the late kick-off against Brighton and Hove Albion.
The return of Ryan Bertrand from a three-month long injury and Pierre Emile Hojbjerg provided a spark for Southampton, with the two nearly linking up for an early chance.
Despite the run of possession throughout the first-half, it was Cardiff who made the crucial breakthrough after halftime when Sol Bamba scored from inside the six-yard box after Callum Paterson nodded the ball down into the area.
Jan Vallery came closer to an equaliser on 76 minutes when he raced past a flurry of defenders before being denied at the last by a steady Neil Etheridge, before Lee Peltier made consecutive blocks on Charlie Austin and Mohamed Elyounoussi.
James Ward-Prowse then combined with Austin from a corner-kick, as the forward’s header was sent across goal and into the path of Stephens at the far post to draw Southampton level.
The jubilation was short-lived, however, as Cardiff regained their lead when Zohore tucked home from inside the six-yard box following a goalmouth scramble.
Southampton: McCarthy, Bertrand, Vestergaard (Elyounoussi), Stephens, Bendarek, Valery (Gallagher), Ward-Prowse, Romeu, Hojbjerg, Redmond, Long (Austin).
Unused subs: Gunn (GK), Yoshida, Targett, Slattery.
Goals: Stephens (90+1).
Bookings: Ward-Prowse (45+1), Redmond (89), Romeu (90+6).
Cardiff City: Etheridge, Bennett, Bamba, Ecuele Manga, Peltier, Paterson, Ralls, Gunnarsson (Bacuna), Arter, Niasse (Camarasa), Reid (Zahore).
Unused subs: Smithies (GK), Hoilett, Mendez-Laing, Murphy.
Goals: Bamba (69), Zohore (90+3).
Bookings: Gunnarsson (61), Bamba (70), Zohore (90+4).