Cash-strapped Racing are 18th in the 20-team table after six games and have yet to win a match since Argentine Cuper, who led Valencia to successive Champions League finals in 2000 and 2001, took over at the end of June.
Their annual budget was around 30 million euros last season, compared with the estimated 500 million each for Barca and Real, and they were forced to enter administration in July.
"It's difficult because we have a very low budget and it's all very tight," Cuper said in an interview published on Barca's website.
"There's no point complaining or crying about what you have and what you don't have," he added.
"We are what we are and we'll fight to meet our goals. I think the other teams [apart from Barca and Real] have very little chance of winning the title."
Cuper, who also coached Inter Milan, said his players had the "desire and enthusiasm" to get a result at the Nou Camp but beating a team he described as "the closest to perfection he had ever seen" would take a lot more than that.
"The current Barca team have so few weak spots," he said.
"Since I've been in the world of football I've never seen anything like them. They're the best team in the world, far ahead of the rest."
RELATIVELY UNSCATHED
While Cuper and Racing are hoping to come away relatively unscathed from the Catalan capital, promoted Real Betis are confident they can cause an upset against Real Madrid at the Bernabeu in Saturday's earlier kick-off.
The Seville-based side are seventh on 12 points, one less than third-placed Real, Malaga in fourth and Valencia in fifth, who all have 13.
Forward Ruben Castro, whose 26 goals helped Betis secure promotion last season, netted a double against Real playing for Las Palmas early in his career and said he was sure his team would score at least once on Saturday.
"We are a great team, we showed it in the second division last season and now in the top flight," he said in an interview published in As sports daily on Thursday.
"Betis is one of the great Spanish clubs and not just any other team that has come up to the first division.
"They [Real] know that and they should be very careful with us. For sure we are going to score."
Surprise package Levante, who are level with Barca on 14 points but have an inferior goal difference, host ambitious Malaga on Sunday.
Valencia play at Real Mallorca on Saturday, when new coach Joaquin Caparros, who replaced Dane Michael Laudrup earlier this month, will make his debut.
