He plays as a right defender and has got 5 assists so far this season for CSKA Moscow in the Russian Premier League. Mário is under contract with Grêmio until March 2014. He transferred to Grêmio from São Caetano in March 2009.
He made his full debut on 28 June 2009, against Sport.
Since then, he has become first-choice right back. Bayern Munich, Manchester United, Juventus, Internazionale, Real Madrid, Football Club Barcelona, F.C.Porto, CSKA Moscow, AFC Ajax and Associate of Science Roma have all been linked with him and he has been dubbed "the new Lúcio".
On 25 April 2012, the Gremio president announced that a 15 million euro deal had been agreed with CSKA Moscow and Fernandes was set to join them pending a medical examination. During the 2013-2014 campaign he suffered a knee injury ruling him out for the first 4 months of the season.
A few days after signing with Grêmio, Brazilian police were called in to search for him after he disappeared.
In 2011 was called to the Brazil squad for the game Superclásico de las Américas and said no, saying he was having "personal problems". Fernandes played 90 minutes, after 64 minutes (2:2) and after one ordinary tackle he was screaming and faked an injury. Referee Paolo Mazzoleni showed Marek Matejovsky the red card.
Russian daily Kommersant wrote it was "An important theatre piece".
Czechoslovakian newspapers said the play was certainly not card worthy and Fernandes lacked fair play. Attributes
He is a tall right-back with good aerial skills and the ability to launch an attack with a long ball.