The Royals have taken just nine points from their first 16 games.
McDermott said: "That's what we have done over the past two seasons - three seasons, actually - so we have got to do that again.
"We know the level we are playing at. We have come up short tonight but we have had a run of five games, four away from home, which is never easy, especially in this division.
"We have to look ahead now, re-group and everybody at the club has to stick together and move on to the next game, which is against Arsenal on Monday night."