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
Eduardo Berizzo has defended Barcelona stars Lionel Messi and Luis Suarez after suggestions they were disrespectful against his Celta Vigo side.
Barcelona forward Lionel Messi is out of hospital and recovering after a non-surgical procedure to cure his kidney problems.
Barcelona have confirmed that Lionel Messi is undergoing further tests on kidney problems which first emerged in December but expect the forward to return to training on Wednesday.
Neymar of Barcelona has claimed that winning trophies motivates him more than being named the best footballer in the world.
Lionel Messi's goal at the weekend saw the Argentine reduce Cristiano Ronaldo lead to five in the pair's head-to-head scoring contest in La Liga.
Real Madrid are football's biggest moneymaker for the 11th straight year, while Bayern Munich dropped to their lowest position in eight years.
First-half goals from Munir El Haddadi and Neymar give Barcelona a slender lead in their Copa del Rey quarter-final tie against Athletic Bilbao with a 2-1 first-leg win.
Cristiano Ronaldo explains to reporters how he helped out his rival Lionel Messi with language issues and now expects to be paid.
Luis Suarez's hat-trick helps Barcelona extend their dominant La Liga record against Athletic Bilbao with a crushing 6-0 victory over the 10-man Basque side at Camp Nou.
Munir El Haddadi score both goals as Barcelona beat Espanyol 2-0 on Wednesday to ease into the Copa del Rey's quarterfinals with a 6-1 victory on aggregate.
