- 2.2.1 Siege
- 2.2.2 finals
- 2.3.1 finals
Oncins 1988 tennis pro, played only in tournaments in his home country. In 1989 he won both his first individual title as well as his first doubles title on the ATP Challenger Tour, the following year he won two Challenger tournaments. In 1991 he won in his hometown at the side of Andrés Gómez his first doubles title on the ATP World Tour. He was also in the singles final of the tournament, losing to Jordi Arrese. His two ATP singles title he won in 1992 at the tournaments in Bologna and Búzios. Overall, he was able to win five doubles titles during his career. Its highest listing in the tennis world ranking he reached in 1993 with position 34 in the singles and 2000 position 22 in doubles.
His best individual result at a Grand Slam tournament was reaching the second round at the French Open in 1992. 's Doubles competition he came twice before the semi-finals of the French Open. In addition, he was in 2001 with Paola Suárez in the Mixed final of the French Open, where they were subject to Virginia Ruano Pascual and Tomás Carbonell.
Oncins played between 1991 and 2001 20 singles and 17 doubles matches for the Brazilian Davis Cup team. His greatest success with the team was reaching the semi-finals of the World Group in 2000, where he double was used in each case. On the side of Gustavo Kuerten he won his doubles match against Nicolas Escudé and Cédric Pioline in the first round and against Dominik Hrbatý and Karol Kucera in the quarterfinals. In the 0-5 semi-final defeat against Australia Sandon Stolle they lost and Mark Woodforde in three sets, each of which was decided in the tie-break.
In the Summer Olympics 1992, he joined Brazil in singles and in doubles. He reached the quarterfinals, where he was Andrei Cherkasov inferior. With sinem partner Luiz Mattar he left, however, from as early as the first round. Four years later at the Summer Olympic Games in Sydney, he joined only in double. Again he came, this time on the side of Gustavo Kuerten, not on the first round also.