Nienov started his career as a goal keeping coach in his native country Brazil in 2001 after completing his university studies. Working for 4 years for Figueirense Football Club, he was with the team as they achieved admission in to the Brazillian Premier League and proceeded to have a run as champions of Santa Catarina State for 3 consecutive years. In 2002 the goalkeeper Edson Bastos was elected by Placar Magazine the second best goalkeeper of the Brazilian Premier League and the third goalkeeper with the least conceded goals.
Over the next 4 years he worked with Sport Club of Recife and Club de Regatas Vasco da Gama where once again, under his guidance and coaching the goalkeeper Magrão was the top goalkeeper with the least conceded goals in the Brazilian First Division with only 36 goals in 38 matches. And in the
Pernambuco Championship was the goalkeeper with least conceded goals as well, with only 7 goals in 18 matches.
In the final match of the Pernambuco Championship, the goalkeeper Gustavo saved three penalties, against Santa Cruz Football Club.
Looking to ply his trade in South Africa, Milton then signed with Free State Stars in 2009 and remained there until 2014 where his coaching helped to reverse their keeper Kennedy from being the keeper with the most conceded goals to eventually be selected as the best keeper in the PSL.
He then moved to Polokwane City for a short period where he once again enjoyed sucess in his time there.