Woeful Manchester United rely on Robin van Persie's class to shoot down Saints
Southampton 1 - Manchester United 2
Louis van Gaal will take his wins however he can get them. Two goals from Robin van Persie and a string of fine saves from David de Gea took United to the dizzy heights of third for the first time since they won the title.
That's five wins on the spin, but Van Gaal will know that this was another unconvincing, often shambolic effort, yielding the prospect of a positive result only when he abandoned his mad obsession with three at the back.
And it was a horror night for Northern Ireland starlet Paddy McNair who was hauled off on 39 minutes after a poor display at the back.
After gifting United an early lead, Southampton emulated Arsenal at the Emirates last month, shredding United's flimsy resistance at will.
It was frankly embarrassing that a coach with Van Gaal's credentials should send out a team in a formation that they demonstrably cannot play.
To his credit he saw the error of his ways after half an hour, and with Van Persie slowly returning to something like the striker that United signed from Arsenal, inflicted on Southampton a third successive defeat they did not deserve.
Ronald Koeman, the Southampton manager, expressed his surprise at the United formation, and the return to the three at the back that gave such encouragement to Arsenal for half an hour at the Emirates.
"Arsenal showed how to play against it for 30 minutes," said Koeman with a smile in his pre-match interview.
He will have noted, too, that was also United's only victory away from Old Trafford this season. Funny old game.
Though still missing long-term injured Jay Rodriguez and James Ward-Prowse, plus play-maker Morgan Schneiderlin, Koeman was able to call on Dusan Tadic, who limped off in the first half in last week's defeat at the Emirates.
That was, of course, the second successive reverse, inviting the doubters to suggest that a bubble was slowing deflating at St Mary's.
The arrival of a brittle United offered Southampton an opportunity to restore morale.
Though United arrived on the back of four straight league wins, only in one did they convince, against Hull, a team in freefall.
Van Gaal resisted the claims of Radamal Falcao, and his wife, who claimed her husband was fit as a fiddle and ready to start.
Well he was up against the returning skipper Wayne Rooney, United's outstanding performer this autumn.
The Colombian rapier took his place on a bench that also included Ander Herrera, yet again the fall guy in Van Gaal's tactical revision.
The temperature on a freezing night was slow to rise. Both teams struggled to find any rhythm.
Indeed it was a mistake that led to the opening goal. A poor pass out of defence by Michael Carrick failed to find its intended target, Rooney.
It didn't matter. Jose Fonte did Rooney's job for him, feeding Van Persie with what was an intended back pass.
The Dutch striker galloped on to the ball and slotted it through Fraser Forster's legs.
Graziano Pelle had a chance to reply immediately but headed tamely wide.
The Italian, so lethal in the early part of the season, cuts a ponderous figure when the goals dry up. He needn't have worried. Help was at hand.
United's early joy was tempered by the loss of Chris Smalling, who limped off after 15 minutes.
Jonny Evans, himself a serial victim of the club's injury hoodoo, stepped tentatively into the fray.
Southampton took advantage with Sadio Mane running through the heart of the visiting defence, only to over run the ball as he advanced on goal.
Pelle was the next in the slot, forcing a save from David de Gea after a simple pass by Tadic.
This was the Emirates revisited.
United were all over the place as Southampton repeatedly ran at United's soft centre.
Steven Davis and Tadic took it in turns to torment and embarrass, with the inevitable equaliser arriving on 31 minutes after a mistake by Marouane Fellaini presented Pelle with the unmissable chance.
The United net duly billowed, Pelle rifling home with his left foot.
Van Gaal responded with a tactical switch, replacing McNair with Herrera. Not only did this give United an extra man in midfield it dispensed with the three at the back nonsense in which only Van Gaal sees value.
It was as if a fog had lifted. The United players looked genuinely pleased to see each other, as one by one they emerged out of the mist, much as they did against Arsenal. It did not mean they would meet the same happy ending, only that disaster was no longer inevitable.
That said United had De Gea to thank for keeping the scores level after the restart, somehow keeping out Shane Long's header.
It was a torrid opening to the second half for United, but at least going forward they looked a more cohesive unit. Ashley Young and Antonio Valencia were threats on the flanks.
But Marcus Rojo was a lucky man to see Pelle scoop a shot over the bar after losing possession on the edge of the United box.
United have become adept at riding their luck. And with Van Persie slowly rediscovering the art of scoring, there is always hope. And so it was with 19 minutes to go that he converted Rooney's curling free-kick, chopping a left-foot volley with the outside of his boot past Forster.
Southampton could barely believe it. They had been the more cohesive and convincing, yet here they were behind again. Pelle brought another fine save from De Gea as they piled forward once more.
With 11 minutes remaining Koeman replaced Long with Emmanual Mayuka, hoping extra pace might do the trick where a poacher's instinct had failed.
Not this time. United held on for another uncertain victory, and Southampton slumped to a third successive defeat.
Southampton: Forster, Clyne, Fonte, Yoshida, Bertrand, S Davis, Wanyama, Mane, Tadic, Pelle, Long. Subs: K Davis, Gardos, Mayuka, Isgrove, Reed, Targett, Hesketh.
Manchester United: De Gea, McNair, Smalling, Rojo, Carrick, Valencia, Fellaini, Mata, Young, van Persie, Rooney. Subs: Evans, Falcao, Januzaj, Lindegaard, Ander Herrera, Fletcher, Wilson.
Substitutes: Southampton: Mayuka for Long 79; Hesketh for Tadic 70; United: Evans for Smalling 18; Herrera for McNair 39; Fletcher for Mata 89
Man of the match: Robin van Persie