The Red Devils rediscovered their miserable tendencies of late 2015 as they looked wholly lethargic and lacking inspiration in attack.
Marouane Fellaini started in midfield for the home side, and from early in the first half, the home side’s fans began to grew frustrated with the Belgian midfielder’s clumsy and somewhat direction-less approach.
While Fellaini was replaced by Mata at the break, bringing slightly more class to proceedings, during the second half, United wholly failed to deliver a coherent, cohesive offensive display.
Indeed, it was Southampton when went closest, as Sadio Mane was blocked after he initially found space in the box, before Victor Wanyama went close with a second-half header.
Ultimately, United were outdone by a set piece, as Adnan Januzaj gave a way a free kick in a dangerous position.
The ball was swung in by James Ward-Prowse, and Charlie Austin—making his debut after arriving from Queens Park Rangers earlier in the window—headed past David De Gea only eight minutes after coming on.
The home fans were furious at the full-time whistle, directing their ire towards van Gaal. Indeed, the defeat represented one of the nadirs of United’s campaign, with a cameo appearance by a mouse—invading the Old Trafford turf—a rare moment of light relief.
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Manchester United Player Ratings vs. Southampton
David De Gea: 6/10
Daley Blind: 6.5/10
Chris Smalling: 7/10
Mateo Darmian: 7/10
Cameron Borthwick-Jackson: 6/10
Marouane Fellaini: 6.5/10
Morgan Schneiderlin: 6/10
Jesse Lingard: 6.5/10
Ander Herrera: 6.5/10
Wayne Rooney: 5/10
Anthony Martial: 6/10
Adnan Januzaj: 5/10
Juan Mata: 6/10
Paddy McNair: 6/10