Saints started 2016 with defeat at Norwich City in a game that hinged on a second-half dismissal for Victor Wanyama.
The Kenyan was shown a second yellow card with 73 minutes on the clock, with Alex Tettey firing in the Canaries' winner just three minutes later.
The first half was open and entertaining, with Shane Long and Jordy Clasie going close for Saints while Norwich striker Dieumerci Mbokani spurned a couple of good chances.
The half-time interval took the sting out of the game until Wanyama was sent off for the second time this season, with the home side duly taking advantage to secure their second home win in a week and consign Saints to another away defeat.
Ronald Koeman had two changes to the side that lost at West Ham earlier in the week, with Jordy Clasie coming in for the suspended Oriol Romeu while Sadio Mané was dropped to the bench after reporting late to the side's pre-match briefing earlier in the day. James Ward-Prowse was his replacement.
Saints started the game brightly, with Shane Long cutting the ball back nicely in the third minute but Steven Davis’s effort was blocked by Ryan Bennett.
Dušan Tadić then planted an excellent cross onto Long’s head, but the Irishman headed over before taking a punch from Canaries goalkeeper Declan Rudd, who had initially been slow to react.
Victor Wanyama then sent a tenth-minute shot well over Rudd’s goal before Saints were given a fright as José Fonte struggled to deal with a bouncing ball, but Jonny Howson miscued his shot and poked wide.
The visitors quickly resumed their dominance, with Tadić excellently picking out the overlapping Ryan Bertrand, who muscled his way past Nathan Redmond and pulled the ball back for Ward-Prowse to draw a smart save from Rudd.
There was another let-off for Saints on the 20-minute mark when, after Wes Hoolahan stole in between Fonte and Virgil van Dijk and laid the ball off for Howson, the former Leeds man’s cross flashed across goal but behind the run of Dieumerci Mbokani.
The Congolese forward went close to opening the scoring on the half-hour mark as a Canaries counter-attack ended with him getting a foot to Russell Martin’s deflected cross, only to divert the ball wide under pressure from Cuco Martina.
Saints immediately went on the attack as Martina’s perfectly-weighted through ball set Long free, but he was denied by a combination of onrushing goalkeeper Rudd and the back-tracking Bennett.
Long was denied again from the resultant corner, with his header from Bertrand’s delivery bouncing off the turf before being tipped over by Rudd.
Van Dijk then headed over from a Ward-Prowse corner, before Hoolahan lofted a shot over the Saints goal after latching onto a Maarten Stekelenburg punch.
Koeman’s men continued to battle for a goal at the end of an entertaining first half, with Clasie being denied his first Saints goal as his fierce drive was excellently tipped wide three minutes before the break.
And yet there was still time for Mbokani to go close once more before the interval, as another Norwich counter resulted in Howson crossing for the striker to flick the ball over Stekelenburg’s goal after finding space.
The second half did not begin with the fervent opening of the first – it wasn’t until Alex Tettey blazed a 62nd-minute left-footer over that either side mustered a meaningful attempt at goal.
Stekelenburg had to be alive five minutes after the hour when Gary O’Neil’s driven corner swerved towards goal, with the Dutchman smartly clawing the ball away from danger.
It took a sending-off for the half to come to life, when Wanyama was shown his second yellow card of the game with 73 minutes gone after clattering into Canaries substitute Vadis Odjidja-Ofoe.
The Canaries quickly made the most of their one-man advantage, as Odjidja-Ofoe beat Clasie before cutting the ball back for Tettey to rifle the ball beyond Stekelenburg just two minutes after Wanyama’s dismissal.
Mané’s exile came to an end soon afterwards, as he and Harrison Reed were introduced in a double substitution for Clasie and Tadić, while Gastón Ramírez replaced Ward-Prowse minutes later.
But the changes were not enough to stop Saints from suffering a fourth successive away loss and to leave Koeman perhaps rueing another first-half showing that perhaps deserved better.
Norwich City (4-2-3-1): Declan Rudd; Russell Martin (c), Ryan Bennett, Sebastian Bassong, Robbie Brady; Alex Tettey, Gary O’Neil; Nathan Redmond (Vadis Odjidja-Ofoe 63), Jonny Howson, Wes Hoolahan (Martin Olsson 81); Dieumerci Mbokani (Cameron Jerome 81). Unused substitutes: John Ruddy (GK), Steven Whittaker, Graham Dorrans, Youssouf Mulumbu.
Goal: Tettey (76)
Bookings: Rudd (88)
Southampton (4-2-3-1): Maarten Stekelenburg; Cuco Martina, José Fonte (c), Virgil van Dijk, Ryan Bertrand; Victor Wanyama, Jordy Clasie (Harrison Reed 80); James Ward-Prowse (Gastón Ramírez 87), Steven Davis, Dušan Tadić (Sadio Mané 80); Shane Long. Unused substitutes: Paulo Gazzaniga (GK), Maya Yoshida, Matt Targett, Ryan Seager.
Booking: Wanyama (35)
Red card: Wanyama (73)
Referee: Mark Clattenburg