Benitez thinks that United have enough quality in attacking areas to rotate and cause his team problems regardless of changes from Sir Alex Ferguson.
He told the club's official website: "It will be a tough game against a good team who are top of the table. It's an away game for us, so we know it will be difficult but we are confident we can go through.
"If you analyse the squad they have, they have four strikers and two players in each position that could play for any team. They have a strong squad and even when they make changes they keep the quality.
"In attack, they have Javier Hernandez, Danny Welbeck, Wayne Rooney and Robin van Persie, and they can play any of them. If you look at the players they have in wide areas and in the middle, especially if they are winning, in the last 20 minutes they still have players like Ryan Giggs and Paul Scholes to bring on also."
Chelsea knocked United out of the League Cup earlier this season but also suffered a 3-2 home defeat to the Red Devils in the Premier League.