United travel to Stamford Bridge without Daley Blind, Phil Jones (both ankle), Michael Carrick (calf) and Marcos Rojo (stomach) following setbacks suffered in their 4-2 win over Manchester City last Sunday.
Those absentees mean that one of Tyler Blackett or Paddy McNair is likely to partner Chris Smalling in central defence.
Speaking at his pre-match press conference, Mourinho said: "Their squad is amazing, in numbers, in players, in experience, their squad is amazing.
"I sat down this week to analyse the opponents and I realise what they have. [Louis] Van Gaal is a fantastic coach to the young players, they are more than ready."
Chelsea are eight points clear of third-placed United in the race for the Premier League title and have the advantage of a game in hand.
"To play against Man United is to play against one of the biggest clubs in the world," Mourinho added.
"This is what everybody wants. This week I was not worried about motivating players because there is no need. It is an easy job."
