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 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
Lionel Messi and hat-trick hero Luis Suarez were in sensational form as they helped Barcelona start their title defence with a crushing
Luis Enrique wants his players to take the plaudits as Barcelona crush Sevilla 3-0 to win their 12th Spanish Super Cup.