Cardenal said he was generally satisfied with Spain's tally of 17 medals in London - three gold, 10 silver and four bronze - which was one less than in Beijing four years ago.
However, he said it was the second Games in a row in which the Iberian nation had flopped in athletics after they also left the Chinese capital in 2008 empty-handed.
"We need to reflect profoundly with athletics; it's not the first time we have failed to win a medal," Cardenal told Spanish radio. "But we are not the only country this has happened to.
"The sudden arrival of emerging countries is also a factor, because in middle-distance running for example until a few years ago it was between the Europeans and the Americans.
"Now countries are dominating who did not pay any attention to the sport before."
Spain have enjoyed spectacular success in high-profile sports such as soccer, tennis and motor racing in recent years but their performances at Olympic Games have disappointed.
After winning 22 medals on home turf at the Barcelona edition in 1992, including 13 golds, the tally has tailed off, with the 11 medals in Sydney in 2000 an embarrassing low.
National Olympic committee president Alejandro Blanco said the parlous state of the economy might be a hindrance to Spain.
"The future will be what the economy allows and if we have the 2020 Games in Madrid we will exceed the 13 golds from Barcelona," Blanco said.
Madrid is one of three candidates, along with Istanbul and Tokyo, bidding to host the 2020 Games. The International Olympic Committee (IOC) will choose the hosts in September next year.