After Chelsea ended their unbeaten run on Saturday, Ronald Koeman’s men could do nothing to stop it becoming back-to-back Barclays Premier League defeats.
Both goals came from Matt Ritchie set-pieces, as Saints struggled to deal with his excellent deliveries. Steve Cook was the beneficiary for the first of those just after the 30-minute mark as he prodded home.
The second game from former Arsenal striker Benik Afobe, as he glanced home Ritchie’s free-kick ten minutes from time to seal the win for the Cherries.
Having played Chelsea just three days previous, Koeman made three changes for the trip to Vitality Stadium as Maya Yoshida, James Ward-Prowse and Sadio Mané all came into the side, while Shane Long was fit enough to start despite coming off injured against the Blues.
Steven Davis, Jordy Clasie and Matt Targett were the three to drop to the bench, with Ryan Bertrand moving to left wing-back as Koeman kept faith in the 3-5-2 formation.
It was down Bertrand’s side however in which the Cherries caused Saints problems early on, as former Portsmouth man Ritchie saw a shot well saved by Fraser Forster.
At the other end Charlie Austin, who had a trial with AFC Bournemouth before joining Swindon Town, perhaps should have done better from Cédric’s cross, but the striker fired just wide of the target.
After a pulsating opening 30 minutes to the game, it was the hosts who struck first. Ritchie’s free-kick, which came after José Fonte had fouled Joshua King, was well saved by Forster, but the ball fell kindly for Cook to fire home.
Such was the home side’s dominance, Koeman was forced into an early change, brining Yoshida off for Davis and switching to a 4-3-3 system, but Saints couldn't conjure up a meaningful chance before the break.
With the start of the second half delayed due to fourth official Kevin Friend collapsing and a replacement being required, Saints were afforded an extra five minutes to construct a game-plan to turn the clash around.
But the first 15 minutes of the second half passed without incident, until Austin was forced off with injury and replaced by Pellè – the striker looking to add to his goal against the Cherries in the reverse fixture at St Mary’s.
It was the Italian who had the first shot of a tepid second half, but his low strike from distance never troubled former Saints goalkeeper Artur Boruc.
It would prove to be another Ritchie set-piece that made the difference. His inviting delivery from the right was flicked on by Afobe and beyond the outstretched Forster.
It was a first defeat in six league games against the Cherries for Saints, who will now need to bounce back quickly when Sunderland visit St Mary’s.
AFC Bournemouth: Artur Boruc, Adam Smith, Simon Francis (c), Steve Cook, Charlie Daniels, Matt Ritchie, Andrew Surman, Harry Arter (Dan Gosling 66), Max Gradel (Marc Pugh 85); Joshua King (Lewis Grabban 70), Benik Afobe.
Unused substitutes: Adam Federici (GK), Tommy Elphick, Sylvain Distin, Glenn Murray.
Goals: Cook (31), Afobe (80)
Southampton: Fraser Forster, Cédric, Maya Yoshida (Steven Davis 34), José Fonte (c), Virgil van Dijk, Ryan Bertrand, Oriol Romeu, James Ward-Prowse, Sadio Mané, Shane Long (Dušan Tadić 70), Charlie Austin (Graziano Pellè 60).
Unused substitutes: Maarten Stekelenburg (GK), Jordy Clasie, Cuco Martina, Matt Targett.
Referee: Mike Dean