Mattar 1985 professional tennis player and was the next year in Rio de Janeiro win his first individual title on the ATP Challenger Tour. He also won at the side of his compatriot Carlos Kirmayr also his first doubles title at the Challenger tournament in his hometown. In 1987, he won his first ATP tournament in Guarujá, the title he successfully defended in the following two years. Also in 1987 he won together with Cássio Motta his first doubles tournament on the ATP World Tour with a final victory against the German double doors from Meinecke and Martin Hipp. Overall, he was seven singles and five doubles titles during his career win. Of his seven individual titles, winning six in his home country, only his last tournament victory he celebrated abroad. Its highest listing in the tennis world ranking he reached in 1989 with position 29 in the singles and in 1991 with position 55 in doubles.
His best individual result at a Grand Slam tournament was reaching the third round at the French Open and the U.S. Open. In the doubles competition, he came three times before the knockout round of the French Open.
Mattar played between 1986 and 1995 31 are singles and seven doubles matches for the Brazilian Davis Cup team. His greatest success with the team was reaching the semi-finals of the World Group in 1992, where he fought out of his six games only four. Since he respectively the first and last individual denied and Brazil was unassailable both in the first round against Germany and in the quarter-final against Italy each with 3-1 lead, the games were not played. Of the four discharged Individually he won none. Brazil finally retired in the semifinals with a 0-5 against Switzerland.
At the Summer Olympics in 1988 and 1992, he joined Brazil in both single and double. In 1988, he retired in the first round against Wally Masur. In doubles, he reached together with Ricardo Acioly the second round, where they were inferior to the French duo of Henri Leconte and Guy Forget. In 1992, he retired again in the first round, this time against Paul Haarhuis. This time was on the side of Jaime Oncins also in a double end in round one by a defeat against the Spaniard Emilio Sánchez Vicario and Sergio Casal.