Barcelona and Osasuna appealed against the decision to play the game on Thursday after it was initially postponed on March 8 following the death of a doctor at the Catalan club, but their pleas were ignored.
Barcelona were 4-2 down towards the end of the match before goals from Robert Lewandowski, Eric Garcia and Raphinha secured their comeback.
The 62-year-old Mazzarri became the second man to be sent packing this season by the ailing Italian champions.
Girona defeated their Catalan rivals for the first time ever in the top flight in a pulsating battle to rise two points above Real Madrid, second, after their 1-1 draw at Real Betis on Saturday.
Champions Barca were dominating the match early on under the scorching heat of south Madrid, with Brazil winger Raphinha the main threat to the home side's defence by running the right channel and creating several opportunities.
Barca's friendly against Juventus, due to be played later on Saturday, was cancelled after an outbreak of viral gastroenteritis among the Spanish team
Xavi's side wrapped up the title after two first-half goals from Robert Lewandowski spurred them to a 4-2 win against city rivals Espanyol on Sunday
UEFA opened a formal investigation into Barcelona last month for potential violation of the European soccer governing body's legal framework regarding payments made by the club to a company owned by a senior refereeing official
Barcelona beat Real Madrid 1-0 in the Copa del Rey semi-final first leg on Thursday at the Santiago Bernabeu, but were criticised for only having 34 percent possession
Lionel Messi and hat-trick hero Luis Suarez were in sensational form as they helped Barcelona start their title defence with a crushing
Luis Enrique wants his players to take the plaudits as Barcelona crush Sevilla 3-0 to win their 12th Spanish Super Cup.
Three points from Barcelona's 3-0 win over Sevilla at the Camp Nou secures the Spanish Super Cup with a 5-0 aggregate victory.
Barcelona captain Andres Iniesta will be out for two weeks after picking up a knock in the the 2-0 first leg Super Cup win over Sevilla this weekend.
Luis Suarez insists the Spanish Super Cup is not Barcelona's yet after helping his team shoot down Sevilla 2-0 to give them a comfortable lead after the first leg of the final.
Argentina fans receive a much-needed boost when Lionel Messi confirmed he would be available for selection.
Barcelona coach Luis Enrique has a tough decision to make before his side's first game of the season against Sevilla in the Spanish Super Cup first leg on Sunday.
Lionel Messi can do extraordinary things with a football but they have not extended to saving the world - until now.
Considered as the best football player in the world and rated by many in the sport as the greatest of all time, Lionel Messi, the La Pulga Atomica gets leveled by his teammates as Barcelona enjoy their bout of bubble soccer.
Barcelona thump English Premier League champions Leicester City 4-2 in a pre-season friendly in Sweden on Wednesday.
