United's interim manager and former striker Ole Gunnar Solskjaer takes his side to Wembley for what is seen as his biggest test to date, having overseen five successive victories in all competitions since the sacking of Jose Mourinho.
British media have enjoyed building up the match as a clash between the two leading candidates for the Old Trafford coaching role, but Pochettino insisted that the motivation was only on racking up more league points against a top-four rival.
"The motivation is already going to be there. When you are a manager or a coach, you cannot be focused on all the rumours," Pochettino, whose side are third in the Premier League, 10 points above United, told reporters.
"Of course United will come to win and for him (Solskjaer) there is massive motivation or challenge to manage Manchester United. For me it's a massive challenge to be at Tottenham.
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"We are people that love to win and hate to lose. It's always about wanting to win. The motivation in the Premier League is already there."
Pochettino also revealed that he was in Barcelona's Nou Camp stadium in 1999 -- when he was playing for Espanyol -- and witnessed Solskjaer's stoppage-time winner for United against Bayern Munich in the Champions League final.
"I have good memories because," he said. "I was with Toni Jimenez (Tottenham's goalkeeping coach). I remember him when he scored the second goal in the injury time and how I shouted.
"We were neutral people watching a fantastic game. But it was unbelievable. On Sunday we are going to meet when 20 years ago I was shouting a goal that he scored for Manchester United and now we are going to play them at Wembley."
United have had all week to prepare for the visit to Tottenham, spending some of it in the Dubai sunshine, whereas Spurs were involved in an intense League Cup semi-final first leg against Chelsea on Tuesday.
Pochettino said that would not be a factor, though, as his side try and complete the double on United, having won 3-0 at Old Trafford in August.
"Of course it will be tough because they arrive in a good level, good momentum, and they had more time to prepare," Pochettino said. "But we will arrive fresh to compete."
Tottenham will be without Eric Dier who is back in training after having his appendix removed before Christmas while fellow midfielder Victor Wanyama is also out with a knee injury.
Brazil forward Lucas Moura, who also has a knee injury, is unlikely to be available but will be assessed.
(Reporting by Martyn Herman; Editing by Christian Radnedge)
