Crewe come into the Cup game on the back of a 4-1 away win at Hartlepool the clubs first away since April and reports suggest that spirits in the dressing room are high.
Thordarson told the official website "It is never an easy game in the FA Cup whoever you play against. It is a one-off game that can go either way on the day.
"We have got to travel to London again and play at Millwall's Stadium, but we will be going there looking to get something from the game. We will take each game as it comes like that and prepare properly, because every game in England is competitive. The players in this country never give up.
"It doesn't make any difference to me that my first game is in the FA Cup. It is a game we will be looking to win for the club and the supporters. Of course, because of where we are in the league, points are our priority but it always nice to get through in the FA Cup also."