Mark Nielsen

Mark Nielsen (born 8 October 1977) is a former professional tennis player from New Zealand.

Career Nielsen had a highest junior ranking of 16th and during his early career on the juniors circuit had wins over Dominik Hrbatý, Mark Philippoussis and Paradorn Srichaphan. At the 1994 Australian Open, Nielsen and partner Jean-Noel Grinda Jr made the boys' doubles semi-finals. He took part in a World Group play-off tie against Spain in 1999, which the New Zealanders lost without winning a match. He competed in the Heineken Open a further seven times and also reached the second round in 2002, with a win over seventh seed and world number 33 Andreas Vinciguerra.

In 2006, a sample that Nielsen had provided while playing the qualifying stages at the Australian Open, tested positive for finasteride, which can be used as a masking agent. An independent Anti-Doping Tribunal accepted Nielsen's claim that he took the product containing the positive substance to treat hair-loss, but found that by failing to check whether the hair-loss product contained such a substance indicated a "serious dereliction of duty on the part of any player who participates in a sport governed by the WADA Code". He was given a two-year suspension by the International Tennis Federation.

The ban effectively ended his career, but once the suspension ended he did briefly return to compete on the Futures circuit and he played a Davis Cup tie in Kuwait. That would be his 20th and final Davis Cup tie, a tally bettered only by Onny Parun. He finished with 25 Davis Cup wins to his name, from 43 rubbers. His 20 wins for New Zealand in singles also has him second all-time, to Onny Parun.

Challenger titles

Doubles: (3)