Hazard was fouled several times in the narrow FA Cup win over United at Stamford Bridge earlier this year.
Ander Herrera was dismissed for two bookable offences in the space of 15 minutes as he twiced tripped Hazard in the United half.
Speaking immediately after quarter-final win at Stamford Bridge, Conte said United made it "impossible" for Hazard to play football.
And the Italian says Chelsea have not prepared for United deploying similar tactics at Old Trafford on Sunday.
"It is very difficult to prepare for this type of situation, we are preparing tactically for this game.
"This game will be very tough for both teams, the result is very important for us and them. But I haven't prepared for this type of situation."