He is happy the pressure is off after ties against League One sides Crawley and Sheffield United in rounds three and four.
McDermott said: "This is the toughest game you can have. If we are going to get into the next round, we are going to have to do it the hard way.
"We played Crawley and were under pressure to win that one, then were favourites against Sheffield United.
"We won't be favourites at Old Trafford, but it is just a fantastic opportunity for our players."