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
Fernandes told BT Sport. "The belief of the fans, they push us through difficult moments. We have made great comebacks, the club is made also by that. In the past we have done a lot like this result"
Mexico's Pumas on Saturday signed Dani Alves after the veteran Brazilian defender left Barcelona for a second time.
Barcelona's reliance on Lionel Messi should not be considered a bad thing, according to former centre-back Patrik Andersson.
Real Madrid forward Cristiano Ronaldo believes that he is the best player in the world ahead of Lionel Messi of Barcelona.
Barcelona star Neymar must focus on more than just the attacking aspects of football if he is to be considered among the greats, says Brazilian legend Pele.
Emiliano Insua says the mere presence of Barcelona forward Lionel Messi makes rivals feel afraid and insecure on the pitch.
Barcelona were held to a scoreless draw by third-tier Villanovense on Wednesday in a disappointing start to the Copa del Rey for the defending champion.
Even a superstar like Messi of Barcelona needs to evolve to stay ahead of the curve especially when he faces stiff competition from Cristiano Ronaldo of Real Madrid.
Barcelona president Josep Maria Bartomeu has responded angrily to reports suggesting Lionel Messi will leave the club, insisting that the reports are "embarrassing".
Injured Barcelona star Lionel Messi has failed to rule out leaving the Treble winners in the future, and has denied he is in competition with Ballon d'Or rival Cristiano Ronaldo of Real Madrid.
Substitute Ivan Rakitic scored twice to earn Barcelona a 2-0 victory over BATE on Tuesday and move the European champions three points clear at the top of Group E.
Sergio Busquets has hailed Barcelona teammate Neymar for his sizzling form on the pitch, but says the loss of Lionel Messi to injury is still being felt within the Blaugrana team.