Thursday's first leg at the Nou Camp will be a first chance for fans to see how new Barca coach Tito Vilanova, who has replaced Pep Guardiola, measures up against the La Liga champions.
"A match between rivals is always important, even in a summer tournament, but the Super Cup is the least important of the four we play during the season," Mourinho told a news conference.
"I believe there is no relation between the winner and what is going to happen in the whole season. We lost the Super Cup last season and we won the league breaking records.
"At Inter [Milan] I also lost the Super Cup and that season we won the treble - the cup, the Champions League and the league - and with Chelsea we won the Super Cup and didn't win the championship."
Barca's stormy 5-4 aggregate win last year marked a low point in relations between the arch-rivals.
Three red cards were flashed after a melee between the players at the end, while Mourinho's infamous finger-in-the-eye attack on Vilanova, who was Guardiola's assistant, led to bitter recriminations from both sides.
There has been a much calmer build-up to the latest clash between the Spanish powerhouses, with the head injury suffered by defender Pepe in last Sunday's league match against Valencia a case in point.
Pepe, who collided heads with Iker Casillas, spent Sunday night in hospital after he lost consciousness and was still being monitored by medical staff after his release on Monday.
During the week Barca defender Gerard Pique tweeted his best wishes to the Portuguese international, a favourite hate-figure at the Nou Camp, wishing him a swift recovery.
"Pepe will not play, it isn't humane to risk a player for a game of football, however important it may be," Mourinho said.
"He is recovering very well and we think he will be back again on Sunday without any type of risk."
With just under two weeks to go to the end of the transfer window, Real have yet to make a major move in the market while the futures of Turkey midfielder Nuri Sahin and Brazil playmaker Kaka are the subject of much media speculation.
Mourinho said he wanted Sahin to go out on loan, ideally to the Premier League with reports saying Arsenal are leading Liverpool in the chase.
"It can teach him particular characteristics of play that he doesn't have at the moment," Mourinho said.
"I couldn't care less if he goes to Arsenal, or Liverpool or Tottenham. I have no preference.
"With Nuri we have proposals on the table, but we have no official proposals for Kaka."
Former club AC Milan had been mulling a bid for Kaka.
