Van Gemerden appeared in all Grand Slams and was also a Davis Cup representative member of the Netherlands team. He ranked nr. 1 player in the Netherlands and reached ATP singles world ranking nr. 100 by June, 2006. He marked the beginning of his career in 1997, with the Dutch Junior Champion under 18, indoor and outdoor titles. In 1998-1999 he comprised the Jong Oranje - a prized contract presented by the KNLTB to Netherlands' most proficient junior players. During a MauritiusChallenger tournament, late in December 2004, he was tested positive for a metabolite of cannabis or tetrahydrocannabinol. Whilst the ATP tribunal accepted Van Gemerden had committed a doping offense under the rules of the Tennis Anti-Doping Program with Exceptional Circumstances; the use of cannabis, in that case, was determined to not be for performance enhancing reasons. It was ruled he forfeit US$2,950 in prize money and all ranking points won at the Mauritius Challenger. Although he was eligible to return to competition immediately, Van Gemerden voluntarily sat out. Coming after, in July 2005, he defeated Kristof Vliegen, triumphing the Scheveningen Challenger. Van Gemerden played for the Netherlands Davis Cup team from 2004-2006. He took on Slovakia in the 2005 World Group quarter-finals and appeared both in the doubles, with Paul Haarhuis, and in the singles against Michal Mertiňák. He lost both of those matches and was also unable to register a win in the two other Davis Cup matches of his career, singles rubbers against Russians Nikolay Davydenko and Dmitry Tursunov in 2006. The Dutchtennis player begin his appearance at Grand Slams starting with the 2005 Australian Open, where he was drawn up against 31st seed Juan Carlos Ferrero, who won the match in four sets. The same year, he was a quarter-finalist in the 2005 Dutch Open, beating world number 46Christophe Rochusen route. The following year, in 2006, he played in both the French Open and Wimbledon Championships. In France he lost in the opening round to Juan Mónaco but he made the second round of Wimbledon, beating Josh Goodall, before being eliminated from the tournament by Mardy Fish. Van Gemerden made it to US OPEN by 2008, being defeated by Jean-Yves Aubone at the first round. Postliminary, in 2008, he began professionally coaching Ana Ivanovic, then ranked nr. 5 of the WTA Tour. Van Gemerden carried as a professional tennis coach until November 2015, instructing the likes of Fernando Verdasco, Sorana Cirstea, and Thiemo de Bakker.
