Portsmouth 2, Manchester United 1.

The strained look on the faces of Manchester United's embarrassed superstars spoke more eloquently than words could ever do as they made their silent exit from a self-inflicted beating at Fratton Park.

Merely being a member of United's all-star cast is a pressure in itself.

But the 2-1 defeat at Portsmouth - only their fourth in the Premiership this season - has left them facing a Premiership title test-of-nerve which manager Sir Alex Ferguson likes to call ''squeaky-bum time'' for anybody bold enough to aspire to the crown they used to regard as their birthright.

Now just three points and a superior goal-difference separate them from Jose Mourinho's Chelsea who have dared to usurp them at the top of the English football tree over the past two seasons.

And Ferguson, despite his inevitable show of defiance, must surely be concerned by the state of the mental strength of his troops at this critical stage of the race for the prize he covets most of all - more even than European supremacy.

Even Ferguson now concedes that, with just six games to go it could all go down to the wire.

And he knows much may depend on how the runners in the two-horse race deal with the demands of their Champions League quarter final tasks tomorrow - United facing a 2-1 deficit against Roma at Old Trafford and Chelsea going to Valencia at 1-1.

United, who face Watford in an FA Cup semi final on Saturday which no longer looks the one-sided spectacle it initially appeared, have their next two league games at home against Sheffield United and Middlesbrough and Ferguson said: ''We have to make the most of that.

''But Chelsea have some tough games, too, in the last six and I can't believe somebody will not make them suffer as well.''

Suffer? Stand-in skipper Rio Ferdinand's countenance after his amazing 88th-minute own-goal clinched the points for Portsmouth said it all.

So did the unmistakable look of boiling anguish in Wayne Rooney after he was rightly denied two penalty claims and wrongly robbed of a certain goal by an offside flag.

The inflammable England striker conducted a running verbal warfare against referee Mark Clattenburg who, ironically, once chalked off a goal against United in a home match against Tottenham.

And he had to be physically restrained from approaching the official at the end of the game.

Ferguson said: ''If it comes down to the last match of the season I will happily settle for that. To be fair to the lads, they have always shown character and I expect them to recover from this.''

Expect a siege-mentality extraordinary from United now. Plucky would-be interviewers trying to approach amiable defender John O'Shea - who scored their last-gasp consolation goal against Pompey - were fended off by a club official who shepherded the Irishman away.

As always United will try to let their talent and resilience do the talking, but Portsmouth manager Harry Redknapp, at least is still backing them.

He said: ''It is going to be very tight now but United have three points in hand and a better goal difference. So you would have to make them favourites.

''They are still a great team and I think Ferguson, hand-on-heart, would say that despite wanting to win everything he can he wants the Premiership title most of all.

''I have no preference about who wins the title. I get on well with both managers am great friends of Fergie and they have boys like Rio and Michael Carrick in the team whom I've known from West Ham days as 13 and 14 year olds.

''My nephew Frank Lampard plays for Chelsea and I would be delighted to see him do it.''

Redknapp wants his Portsmouth team to repeat their performance against Watford today as they bid to return to the Premiership's top seven.

He said: ''They will look to do to us what we did to United. And we need people to stand up strong and head it away but we have shown again what we are capable of doing - and we have to do it again.

''I have never known three easy points in the Premiership and it looks like we are going to be without key players ."