Fined by the club on Friday after arriving late at the team hotel following a day off, Ronaldo was surrounded by admirers and needed the help of security staff to force his way out of the stadium at the end of the game.
Modest Marilia went ahead with a goal from Fabiano Gadelha in the 38th minute and Jorge Henrique headed the unimpressive Corinthians level just after the hour mark.
The Paulista is the largest of the regional championships which act as a prelude to the Brazilian championship.
In the same competition, Brazilian champions Sao Paulo slumped to a 1-0 defeat at Santos where Colombian Mauricio Molina scored the game's only goal in the 40th minute.
In the Rio Grande do Sul championship, Internacional stretched their unbeaten run against arch-rivals Gremio to six games, winning 2-1 in the Porto Alegre derby, one of the biggest fixtures in Brazil.
Magrao headed the winner for Internacional with eight minutes left to clinch victory in the first stage of the tournament. The game produced 10 yellow cards and a red for Gremio midfielder Adilson.
Botafogo beat rank outsiders Resende 3-0 to win the first stage of the Carioca championship in Rio de Janeiro.
