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
Barcelona defender Javier Mascherano extended his contract with the Catalan giants until 2019 on Monday.
Argentina's pain is Barcelona's gain as Lionel Messi returns for the Spanish champions when Deportivo la Coruna visit the Camp Nou on Saturday after being sidelined for three weeks with a groin injury.
Barcelona coach Luis Enrique makes no excuses after they lost 4-3 at Celta Vigo and missed the chance to top La Liga.
Messi junior will be one of the first to take part in Barcelona's pilot programme aimed towards the 3-5 year age bracket.
Ronaldinho is back at Barcelona as an ambassador for their New York office.
Barcelona are on the verge of completing a reported 30 million euro move for Spain international Paco Alcacer from Valencia.
Barcelona coach Luis Enrique highlights the hunger of his squad not to be ousted by Real Madrid as Spanish champions after a hard-fought 1-0 win at Athletic Bilbao.
Lionel Messi has won the UEFA Goal of the Season award for a brilliantly worked strike against Roma in the Champions League.
Argentina great Diego Maradona criticises Lionel Messi, suggesting that the Barcelona star's retirement from international football, and subsequent change of heart, was "staged".
Claudio Bravo was pictured leaving Barcelona Airport on Tuesday and his expected move to Manchester City is likely to trigger
