4 seed he finished runner-up to Nicola Pietrangeli in the singles final of the French Championships at Roland-Garros in 1959,[2] after having reached earlier in the season the Hamburg International German Tennis Championships final, losing to William Knight.

His best result at the Wimbledon Championships was in 1960 when he reached the fourth round in the singles event which he lost in five sets to Ramanathan Krishnan.

[3] Vermaak competed for the South African Davis Cup team in six ties between 1953 and 1960 and compiled a record of five wins and seven losses.

[4] In 1956 he won the singles title of the South African Championships, defeating Torsten Johansson in the final in five sets.

[5][6] In 1960 he won the Turkish International Championships defeating Fred Stolle in the quarterfinal in five sets, thrice-defending Luis Ayala in the semifinal, and Jorgen Ulrich in the final.