Often seen as a gentleman’s sport, tennis isn’t always marked by exemplary sportsmanship. Austrian Daniel Koellerer, who once ranked as high as World No. 55, was notorious for his aggressive behavior both on and off the court. Known as “Crazy Dani,” he sparked numerous controversies and even directed criticism at top players, including Rafael Nadal. In 2011, Koellerer made history by receiving a lifetime ban from professional tennis.
Early Career and Rise to Prominence
Born on August 17, 1983, in Wels, Austria, Koellerer began his junior career with notable victories over future Top 10 players like John Isner and Jo-Wilfried Tsonga in 2001. He turned professional the following year and steadily built his ranking through the Challenger Tour.
In 2009, Koellerer achieved his first Top 100 ranking, reaching No. 85 after winning a Challenger event in Rome. Tragically, his mother passed away from cancer during the same week, and he dedicated his victory to her memory. By October, he had pushed his ranking to a career-high of No. 55.
Daniel Koellerer playing in 2010 (Matthew Stockman/Getty Images)
Controversial Behavior and Peer Reactions
Koellerer’s behavior made him a polarizing figure in the tennis world. According to several reports, the ATP suspended him twice for on-court misconduct in 2004 and 2006. The latter suspension lasted six months, but Koellerer’s antics did not stop there.
His controversial ac
