كتب : Karim Farouk
United goalkeeper Edwin Van Der Sar are to blame for this critical loss while his counterpart David James produced one of his best performances to grab his side a precious victory.
Pompey went ahead when the Dutch keeper could only parry, awfully, Benjani's shot and Matt Taylor followed up to score from inside the box.
Manchester United tried to pull back but the home side got back in defense and could specially control Portuguese on fire forward, Cristiano Ronaldo.
Sir Alex Ferguson threw more attacking cards as Ryan Giggs and Ole Gunnar Solskjaer were brought into action to replace Kieran Richardson and Darren Fletcher.
The visitors put Pompey under a huge pressure and had a lot of chances that were mostly denied by some heroics saves from David James.
Van der Sar matched James's heroics with a brilliant flying stop to turn Sean Davis's 65th minute volley around a post and deny the midfielder his first goal of the season.
And while Manchester seemed to be close from the equalizer, the Dutch international conceded a crucial second goal when he needlessly came racing out of his goal and allowed Ferdinand's back pass to trickle past him for an own goal.
The Reds quickly reacted with a goal from John O’Shea one minute later but it was not more than a consolation goal.
Otherwise, Arsenal conceded their first defeat at the Emirates Stadium from West Ham 0-1, while Liverpool got through Reading 2-1.