The Pompey boss believes this could be the only way of securing a shock result against the Barclays Premiership leaders, who are looking to take another step towards wresting the title from Chelsea's grasp.

Redknapp is convinced opposite number Sir Alex Ferguson will field his strongest side at Fratton Park rather than save key players for Tuesday's Champions League quarter-final return against Roma.

He said: "I know Alex wants to win every trophy he can but, if he was pressed, I think he would have to admit that the Premiership title is the one he wants most of all.

"I've heard it said that he will rest several players for Saturday's game because of the European situation but I think that is bull.

"He has built a great new side there now with players like [Wayne] Rooney and [Cristiano] Ronaldo, who can cut you to pieces and they are people who can tear you to pieces if you let them play.

"I heard Kanu get some stick last week at Fulham but that really upset me because he has done a great job for us, scored 12 goals and been brilliant.

"But you have to look at games as they come along and any match against United you have to approach differently to others."

Redknapp's plan would be to flood the midfield and stop United creating opportunities for their lethal frontmen - the most potent attack in the Premiership.

He has used that system before this season even though his instinct is to play an expansive game - particularly at home.

Pompey fans who saw their favourites beat United two seasons running at Fratton Park before last term's 3-1 home reverse may want to see them attack the visitors but Redknapp, as always, is a realist.

He said: "Let's face it, whenever you get something from one of the top four, it is a real bonus.

"We are not scoring too many goals lately but our defence is strong and we have to play to our strengths with determination and belief."

Midfielder Pedro Mendes is the only long-term casualty at Pompey with damaged ankle ligaments, but Glen Johnson may also miss out again on Saturday with the knee injury that kept him out of Saturday's 1-1 draw at Craven Cottage.

Tomorrow's game will see goalkeeper David James again go for a record 142nd Premiership clean sheet but he insists: "I will happily wait another day for that if it means beating United 2-1.

"Even a goalless draw would do nicely but the important thing is to believe we are capable of a result in games like this."