Manchester Utd 2 Southampton 1:Manchester United put their foot down to accelerate away from Manchester City and again stretch their lead at the top of the Premier League to seven points with this victory.

On 75 minutes Robin van Persie thought he had made it 3-1 with a strike from Wayne Rooney’s cross delivered with the outside of the England forward’s right boot. But this was ruled offside, though the decision appeared marginal. If the goal had stood a finish that included David De Gea redeeming himself for Southampton’s opener with a fine save from Rickie Lambert’s free-kick would have been less frantic.

United were rocked almost instantly by the kind of howler all managers detest. Addressing a run of league fixtures that began with this one and, Everton apart, included the lesser lights of Fulham, Queens Park Rangers, Norwich City, West Ham United, Reading and Sunderland, Alex Ferguson wrote:

“Let’s not fool ourselves into believing that we are now entering a phase against the lower teams that will present us with easy pickings. That would be a rubbish attitude.”

Rubbish might have been the manager’s description of the start of the game. He had hardly been seated for two minutes when Michael Carrick’s poor back-pass was compounded by de Gea whose indecision meant he stuck out a tentative leg and failed to clear. Jay Rodriguez made it 1-0 from a tight angle.

Within five minutes United were level. Carrick, who redeemed himself from blame for the goal to snap into the tackle and zip around midfield, played a ball that hit a Southampton player and fell to Shinji Kagawa. The Japan forward slid a pass in behind the defence and Rooney slotted it confidently past Artur Boruc.

Swarmed all over

Now United swarmed all over the visitors and by 26 minutes were ahead, Rooney again the scorer. When Van Persie swung a free-kick in from the right that was placed on Patrice Evra’s head, the left back glanced the ball back across goal and Rooney tucked it into the net.

The lead had been coming. Before and after Rooney’s second, United had piled up squandered chances. Kagawa hit Boruc’s right post from close range after Rooney dinked the ball through to him.

Ferguson had made four changes from the team that had trounced Fulham 4-1 here on Saturday. In came Nemanja Vidic, Danny Welbeck, Kagawa and Van Persie, for Rafael Da Silva, Nani, Ryan Giggs and Javier Hernandez.

Mauricio Pochettino, whose second game in charge of Saints this was following the sacking of Nigel Adkins, spent the half standing up in the technical area and could be pleased with his side’s start and how, after soaking up pressure, they threatened to score again.

A ball down the right from Jason Puncheon that found Gaston Ramirez – who had earlier blasted a 20-yard free-kick over – and put him momentarily beyond United’s rearguard offered a warning.

Low save

But then so at the other end had Welbeck’s shot which forced Boruc into a low save. At the break Southampton were fortunate to be trailing only by one.

Pochettino made changes for the second half, replacing Puncheon and Ramirez with Steven Davis and Adam Lallana. In that quest the visitors began brightly and Lambert had a shot saved by De Gea low to his right to begin the half. Then, some close-quarter triangular passing routines were executed impressively by Morgan Schneiderlin, Lambert and Rodriguez as Southampton moved swiftly down their right.

Next, Welbeck conceded a corner under pressure from Clyne which Schneiderlin took and when it was cleared a dawdling Rooney was dispossessed and Saints won another corner.

Once again Schneiderlin floated it in from the right and this time he found Lambert with a yard of turf to himself but the captain failed to capitalise.

As Southampton continued to plug away De Gea was culpable for another nervy moment for United. A 25-yard free-kick was hit straight at him but he spilled it and he was fortunate not to concede the equaliser.

MANCHESTER UNITED: De Gea, Jones, Smalling (Ferdinand 63), Vidic, Evra, Welbeck, Carrick, Anderson (Da Silva 68), Kagawa (Nani 73), Rooney, van Persie. Subs not used: Lindegaard, Valencia, Cleverley, Buttner. Booked: Vidic, Da Silva.

SOUTHAMPTON: Boruc, Clyne, Yoshida, Hooiveld, Fox (Shaw 78), Schneiderlin, Cork, Puncheon (Steven Davis 46), Rodriguez, Ramirez (Lallana 46), Lambert. Subs not used: K Davis, Lee, Richardson, Chaplow. Booked: Schneiderlin.

Referee: Lee Mason (Lancashire).

Guardian Service