Manchester United boss Sir Alex Ferguson said his side were lucky to beat Southampton, describing the visitors' second-half display as the best at Old Trafford this season.
Saints took an early lead through Jay Rodriguez, but two first-half goals by Wayne Rooney sealed victory.
"For the first 30 minutes we were fantastic," Ferguson told BBC Sport.
"But in the second half Southampton have been the best team to play here this season. We were fortunate to win."
Rooney's goals took him to 12 for the season, while Shinji Kagawa also hit the post in the first half as the hosts recovered from a dreadful start to take a seven-point lead at the top of the Premier League.
Michael Carrick's backpass failed to reach David de Gea as Rodriguez stole the ball to score from a tight angle.
And in the second half, Southampton caused Ferguson's team all sorts of problems as they harried the United defence and De Gea was drawn into a fine save from Rickie Lambert's free-kick.
Ferguson also blamed the Old Trafford pitch as United struggled with their passing.
"We found the pitch difficult to play on. Southampton won a lot of 50-50s as our players looked to take a touch," he added. "The Newcastle and West Brom games killed the pitch - it became a paddy field.
"We watered the pitch before the game but once it dried out in the second half it became difficult. They pushed on top of us and didn't give us any time on the ball."
Former Espanyol coach Mauricio Pochettino, in his second game in charge, had prepared his players for this match by taking them to Barcelona where they visited the Spanish giants, so often a thorn in Manchester United's side.
And his side caused havoc in the United defence by adopting a similar high-pressing approach to the Barcelona team that beat United in the 2009 and 2011 Champions League finals.
"I'm very proud [of Ferguson's praise]. It's very important for my players to hear," the Argentine told BBC Sport. "But we leave with no points. We did play well but I'm upset at not getting a draw at least. It doesn't console me."
Pochettino, who said he would make a final decision about transfer targets on Thursday, added: "Taking into account the second half we should have had at least a draw. And once we scored the goal we should have been able to control the game.
"We should have been a lot more aggressive and neutralised their attacking chances a lot more."
Defeat for Southampton ends a six-game unbeaten run but there were encouraging signs for the Saints, who are three points above the relegation zone going into their next game against Wigan.
"In the second half we were dominating and we were taking the game to [United]. We were just a bit unlucky in front of goal," Pochettino said.
"The way we went forward is the way we want to continue. [Pressing high] is the way we want to play, but in the first half perhaps we weren't able to do so.
"I'm proud of the way we played in the second half and that performance will give my players confidence to play on like that in the future."