Flamengo fitness trainer Fernandez reportedly reprimanded Pedro in the dressing room at the Raimundo Sampaio Stadium about his poor attitude after the player sat on the bench unhappy about not coming on as a substitute during the Serie A match.
Pedro alleged that Fernandez punched him in the face.
Both men were later seen arriving at a police station in Belo Horizonte and local media reports said Pedro had filed a formal complaint against Argentine coach Fernandez.
"I could be here talking about the limited play I've been getting in recent games but what happened today was more serious than what can happen inside the pitch," 26-year-old Pedro wrote on his Instagram account on Sunday.
"Cowardly, without reason and inexplicably, I was attacked with a punch in the face by Pablo Fernandez, a member of Sampaoli's coaching staff.
"The physical cowardice has outweighed the psychological cowardice I have suffered in recent weeks."
The fitness trainer apologised on social media, acknowledging the incident and explaining that he reacted in a "high-stress situation", while Flamengo's Argentine coach Jorge Sampaoli expressed his feelings about the incident on his Instagram account.
"I don't believe in violence as a solution. It gets us nowhere. Not in life, not in football," he wrote.
"What happened yesterday made me very sad. We overshadowed an impressive victory with an internal dispute whose reasons exist, but at this moment do not matter."
Pedro has made a name for himself at Flamengo with 93 goals in 192 games since joining from Italy's Fiorentina in 2020.
He helped the Rio de Janeiro club win the Copa Libertadores last year as the team's top scorer in the tournament.
The forward has scored four times in 13 league games this season but his last goal came against Gremio on June 11, five days after he last played the full 90 minutes.
Flamengo are second in the Brazilian league standings, 12 points behind Botafogo.
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