Real host their arch-rivals for a King's Cup quarter-final first leg having won 22 of their last 23 matches in all competitions, the one defeat being a 3-1 La Liga reverse at Barca's hands at the Bernabeu six weeks ago.
Mourinho has managed only one victory over Barca in eight attempts since taking the job two years ago, Cristiano Ronaldo nodding an extra-time winner in a 1-0 triumph in last season's King's Cup final.
Four defeats and three draws across four competitions make up the rest of the story but the coach goes into Wednesday's tie holding a five-point La Liga lead over the champions.
Mourinho has made it clear the league is this season's priority and he would be able to write off a King's Cup slip-up as irrelevant.
However, the psychological impact of the clasico tussles could play a big role in each team's campaign.
"You'll have to ask the Madrid players if we have eaten into their morale," Barca midfielder Xavi told a news conference on Monday.
"Winning or losing will have a big effect on a team's state of mind. The winner will receive a huge confidence boost."
Spanish international Xavi responded to questions about Ronaldo, who has gone off the boil in recent games and received whistles from some sectors of the Bernabeu crowd since his below-par showing at last month's clasico.
The comparisons with Lionel Messi, crowned World Player of the Year for the third time last week, appear to weigh heavy on the Portuguese forward who has scored three times in 10 clasicos compared to the Argentine's seven strikes over the same period.
"Messi always makes the difference. The Bernabeu seems to be to his liking. He always rises to the occasion and we expect him to do the same again," Xavi said.
RUNS OF FORM
"Ronaldo, like all strikers, goes through runs of form. Sometimes the ball goes in, other times it doesn't but it is clear he is capable of making the difference."
Ronaldo is La Liga's leading scorer with 21 goals but his anxious performances against Barca and a tense relationship with some of Real's fans mean the world's most expensive player will once again be the focus of attention.
"I have a routine before matches like most players," Ronaldo told DT magazine. "I try to laugh, crack a few jokes, listen to house music.
"I don't put myself under pressure. If you do this, things go badly. I am this way whether I am preparing to play Barcelona or any other team. My mental strength is very important."
Mourinho has a doubt over defender Pepe, who missed training on Monday with a bruised thigh, but Angel di Maria is expected to return to the squad.
Barca coach Pep Guardiola is without the injured David Villa, Ibrahim Afellay and Pedro while Seydou Keita is away at the Africa Cup of Nations.
On Tuesday third-tier Mirandes, who have knocked out La Liga sides Villarreal and Racing Santander, visit Espanyol.
