Cruzeiro fire Avila after 22 days
Mancini himself was fired by Ceara earlier this month, having been at the helm for five months.
"Mancini's contract is until December. Emerson Avila will return to his previous job as technical co-ordinator," said the Belo Horizonte club on their website.
It was the 30th coaching change of the year among Brazil's 20 first division clubs.
The decision came one day after a 3-0 home defeat by Brazilian championship leaders Vasco da Gama.
Angry fans protested on the terraces and fought with police, while on Saturday around 250 Cruzeiro fans gathered in front of the team's training ground to remonstrate with the players over results.
Cruzeiro began the year with Cuca in charge and he was replaced by former South Africa coach Joel Santana, who lasted three months.
Corinthians, Coritiba, Flamengo and Palmeiras are the only first division clubs to have avoided changing coaches this year. At the other end, struggling Atletico Paranaense are on to their fifth coach.