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 boss Luis Enrique launched a staunch defence of his players after they came from behind without the injured Lionel Messi to beat Bayer Leverkusen 2-1 on Tuesday.
Barcelona were beaten for the first time in La Liga this season as Celta romped to a stunning 4-1 victory at Balaidos on Wednesday.
Catalonia may not be a state, but it can count on a small and symbolic red and blue army in the form of European football champions Barcelona.
LFP president Javier Tebas has said that Barcelona and Espanyol would be unable to play in La Liga if Catalunya becomes independent from Spain.
Barcelona coach Luis Enrique says that Lionel Messi's penalty issues do not make the Blaugrana superstar seem any less of a visitor from another planet.
Cristiano Ronaldo can move ahead of Raul as Real Madrid's top goalscorer of all time as Los Blancos take on Athletic Bilbao.
The Barcelona star has hinted that there is more magic to come after he celebrated 100 games in Champions League.
Cristiano Ronaldo led Real Madrid will battle for supremacy with Barcelona and Argentina forward Lionel Messi.
Lionel Messi will never leave Barcelona, according to the club's sporting director Robert Fernandez.