Dusan Tadic netted a second-half penalty to hand Southampton a 1-0 win at struggling Sunderland in the Premier League on Saturday.
Yann M'Vila made a rash sliding tackle on Ryan Bertrand close to the byline on 69 minutes - one that saw Sam Allardyce put his head in his hands - and Tadic duly slotted home the spot-kick.
Sunderland have now lost three of their four matches since Allardyce took over and remain in the relegation zone on just six points after 12 games.
Meanwhile, Southampton are unbeaten in eight games in all competitions and have yet to taste defeat away from home in the Premier League this season.
Sunderland conceded six goals at Everton last weekend and Allardyce warned his players in midweek that they would need to improve defensively in order to yield more points.
Allardyce handed young striker Duncan Watmore his first Premier League start in one of four changes to the team that were humbled on Merseyside. He started on the left wing as the hosts set up with strong foundations in a very defensive shape - it was a plan that restricted the visitors to just a couple of chances in the opening half.
Southampton striker Graziano Pelle's unselfish flick allowed Tadic a sight of goal from close range on nine minutes but Costel Pantilimon was quick off his line to make the block.
Pantilimon was called into action 11 minutes later as Sadio Mane unleashed a snap-shot from 15 yards that needed punching clear.
Sunderland needed more attacking inspiration after creating next to nothing in the first half and Allardyce sent on Fabio Borini at half-time in search for goals.
However, it was the visitors that kept up the pressure. DeAndre Yedlin, on-loan from Tottenham, made a brave header on his goal line after Jose Fonte flicked a header towards the bottom corner following a Tadic corner.
Sebastian Coates was the next Sunderland defender to make a goal saving block on 61 minutes when he got his right boot to a Steven Davis effort that had Pantilimon beaten.
But it was M'Vila's costly error just after the hour mark which allowed the visitors the chance to go ahead.
Bertrand made a scampering run down the left-hand side of the box and was brought down by M'Vila's clumsy challenge, prompting the referee to point to the spot.
Tadic duly stepped up and whipped the ball into the far corner.
Sunderland responded well, though, and Borini tested Maarten Stekelenburg with a powerful half-volley that on-loan Fulham goalkeeper tipped over the crossbar before Adam Johnson whipped a 25-yard free-kick just wide of the post.
Allardyce's men continued their forward momentum and had appeals for a penalty turned down late on when substitute Jack Rodwell's header hit Maya Yoshida on the arm, but their late charge was in vain.
Phil Thompson's Soccer Saturday verdict
"Southampton really dominated this game from start to finish. They passed the ball better and there were moments they were trying to walk it in. Sunderland, when they lost the ball, backed off into their own half and tried to shuffle across trying to get close down. You were wondering if Southampton scored early it could have been anything but it didn't and they held out.
"Very few of the Sunderland players actually argued with the referee about the penalty decision."
Player ratings
Sunderland: Pantilimon (7), Jones (7), Kaboul (7), Coates (7), Yedlin (7), M'Vila (5), Gomez (5), Toivonen (6), Johnson (6), Watmore (6), Fletcher (5).
Subs used: Rodwell (6), Borini (6), Defoe (6).
Southampton: Stekelenburg (7), Yoshida (6), Fonte (7), van Dijk (7), Bertrand (7), Ward-Prowse (7), Clasie (7), S. Davis (7), Mané (7), Tadić (7), Pellè (7).
Subs used: Romeu (6), Juanmi (6), Caulker (6).
Man of the match: Dusan Tadic