After the abysmal 5-1 defeat to Chelsea, McClaren said: "The majority of the goals and opportunities were self-inflicted."
He defended the trip to La Manga, insisting the 18-day gap between games was an opportunity to regroup and the only way to play a game, against Norwegians Lillestrom.
He added: "During the game and at half-time all the anger and disappointment and frustration has already been expelled.
"Now in the cold light of day we have to be reflective, calm and we have to know that there are 12 games to go.
"It's a good opportunity to regroup, get organised, stay calm, be stable, don't let this derail us.
"The 18 days are good. We have to stick together in that dressing room.
"There's enough quality in there. We have to show character and fight."