Ondruska grew up as a child of Czechoslovakian parents in South Africa. He was a professional tennis player in 1989 and won in the same year in Durban his first Challenger tournament. The following year, he also won a first Challengerturnier in doubles. In 1992 he stood for the first time in the final of an ATP tournament in only once discharged Cologne Open in Cologne, he was defeated Bernd Karbacher in two sets, and on his way to the semifinals of the Miami Masters 1993, he beat Michael Chang and Michael Stich. Overall, it was three times in the final of an ATP tournament, but none could decide for themselves. In doubles, he was much more successful, in 1996 alone get him on the side of changing partners three tournament victories, his last victory he celebrated in Long Iceland, which he won with David Prinosil. Its highest listing in the tennis world ranking he reached in 1993 with position 27 in a single 34 in doubles.
His best individual result at a Grand Slam tournament was reaching the second round at the Australian Open 1996. In the doubles competition, he reached in 1993 on the side of John Laffnie de Jager the semifinals of the Australian Open.
Ondruska played between 1993 and 2001 21 single and a double batch for the South African Davis Cup team. In 1995 and 1996 he was with his team in the quarterfinals of the World Group, both went 4-1 each lost. He was only able to one, against the Italian Renzo Furlan decide of its four individually for themselves. In general, his balance was positive, his only use in the double he could win on the side of Wayne Ferreira, his individual account was 12-9. In the Summer Olympics 1996, he went to South Africa and was eliminated in the second round against Christian Ruud, having previously triumphed against Goran Ivanisevic.