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
Neymar could follow FC Barcelona fellow star Lionel Messi to court after Spanish prosecutors asked for the Brazilian striker to be tried over his murky multi-million-euro transfer to the Catalan giants.
Argentina football star Lionel Messi says he trusted his father with his finances and "knew nothing" about how his wealth was managed as he took the stand at his tax fraud trial.
The trial of Argentina and Barcelona footballer Lionel Messi on tax fraud charges is due to start in Spain.
Lionel Messi must shrug off the gruelling demands of a globe-trotting schedule if he is to fulfill his dream of leading Argentina to a first major tournament victory in 23 years at the Copa America Centenario.
Lionel Messi has been cleared of serious injury after hurting his ribs and back in Argentina's final Copa America Centenario warmup fixture on Friday.
Barcelona striker Luis Suarez is a doubt for next month's Copa America after hobbling off in tears midway through the Copa del Rey final win over Sevilla Sunday with a muscle injury.
A Spanish judge on Friday overturns a controversial ban on Barcelona fans flying Catalan separatist flags at Sunday's Copa del Rey final against Sevilla in Madrid.
Atletico Madrid coach Diego Simeone hails Antoine Griezmann as "one of the best three players in the world" as Atletico prepare to face local rivals Real Madrid in next Saturday's Champions League final.
Barcelona agreed a "long-term" contract extension with American sportswear giants Nike on Saturday, which will reportedly see the Catalan club surpass Manchester United with the most lucrative kit-sponsorship deal in the world.
Real Madrid player Isco shares his admiration for Barcelona superstar Lionel Messi while speaking to the radio channel 'El Hormiguero 3.0' on Antena 3.
