Tennis is often considered a “gentleman’s” sport, but players don’t always display sportsmanship. Austrian Daniel Koellerer, a former World No. 55, was known as “Crazy Dani” for his on- and off-court antics and controversies, including criticizing top players such as Rafael Nadal. In 2011, he became the first player in history to receive a lifetime ban.
Koellerer was born on August 17, 1983, in Wels, Austria. He had a successful junior career, defeating future Top 10 players such as John Isner and Jo-Wilfried Tsonga in 2001. He turned professional a year later and steadily climbed the rankings while competing on the Challenger Tour.
In 2009, he broke into the Top 100 for the first time, reaching World No. 85 after winning a Challenger event in Rome. However, that same week, his mother passed away from cancer. He dedicated the win to her. Later that year, he achieved his highest ranking of No. 55 in October.
Over eight years on tour, Koellerer became known as one of the most provocative players in tennis. According to ESPN, the ATP suspended him twice for on-court misconduct, in 2004 and 2006. The latter suspension lasted six months, but his antics didn’t end there.

Daniel Koellerer playing in 2010 (Matthew Stockman/Getty Images)
He was ‘hated’ by his peers
Koellerer was involved in multiple controversies. According to We Are Tennis, he earned the nickname “Crazy Dani” after competing on the South American Challenger circuit in 2006. Journalist Kamakshi Tandon of ESPN reported that his peers were so frustrated with his behavior that they “took the unprecedented step of circulating a petition to have him thrown off the tour.” Koellerer admitted that 75 out of 80 players signed it.

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According to several reports, he was once punched by the late Federico Luzzi after spitting into his palm before a post-match handshake. In 2010, Brazilian player Marcos Daniel accused him of racism, claiming he called him a “monkey” and told him to “return to his jungle.”
That same year, Austrian compatriot Stefan Koubek nearly strangled him during a national championship match, claiming Koellerer had insulted him. “All the players hate him,” Koubek told We Are Tennis. Koellerer acknowledged his bad reputation but remained indifferent: “I don’t care because I know I already changed a lot, and I will not change for any tennis player. If I change, I change for myself.“
Koellerer said he was taught to provoke
In an interview with ESPN, Koellerer revealed that his first serious tennis coach encouraged him to be confrontational. “What I do sometimes now on the tennis court is because I got taught it… to provoke, to show [the] opponent the fist, to make s— on the court,” he said. “When I didn’t do it, he was pissed. I had to practice more; I had to go to the gym on the bicycle; I had to run one hour more.”
He also said he was bullied as a child at a tennis club in Linz, Austria—not just by other students but also by his coach. Eventually, he punched one of his bullies and switched coaches. “Mentally, it made me tough,” he said. “But it also took me down, because I had this s— all the time in my head.”

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Match-fixing suspension: ‘The ATP Ruined My Life’
In 2011, the Tennis Integrity Unit (now the International Tennis Integrity Agency) found Koellerer guilty of three violations of anti-corruption rules, including “contriving or attempting to contrive the outcome of an event.” He was banned for life.
Koellerer denied all charges, calling them “nonsense.” However, in 2010, he had already been placed on two years’ probation after his website featured match odds and links to betting sites, violating ATP rules.
The Court of Arbitration for Sport (CAS) upheld his lifetime ban in March 2012 after he appealed, though it overturned a fine since he had not financially benefited from match-fixing.

Koellerer during the 2009 US Open (Matthew Stockman/Getty Images)
In 2016, after the BBC and Buzzfeed published a report on match-fixing in tennis, he told Tennis Circus that he had been approached three times to fix matches but refused each time. “I was approached by an intermediary, once I was called into a hotel room, and once they spoke to me at dinner. For a game against [Nikolay] Davydenko, they offered me $50,000—same for a game with [Janko] Tipsarevic. Once, they even offered $100,000 to lose against [Nicolas] Massu. I immediately refused,” he claimed.
“I was pretty stupid on the tennis court—destroying rackets, insulting referees. I was just undisciplined, but I had nothing to do with the scams,” he added. “The ATP destroyed my life. My house, my wife, and my child—everything was gone, and I was depressed. In doping cases, players are suspended for a fixed term. Yet I was condemned without proof for match-fixing,” he said.

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Criticism of Nadal and other top players, and departure from tennis
After his suspension, Koellerer suggested Rafael Nadal had used performance-enhancing drugs. “Nadal cannot be negative. After seven months off due to injury, he returned and won 10 tournaments out of 13. It’s impossible, impossible! Nobody believes he doesn’t take anything. But imagine what it would mean for tennis if Nadal tested positive,” he told Sportwoche in 2013 (via We Are Tennis).
In a 2016 interview with Tennis Circus, he also accused the ATP of protecting top players from punishment. “What is shocking is that it is said that the best four players are involved [in match-fixing]. Personally, I do not believe it. With their bank accounts, they wouldn’t even notice the difference from selling a game.”
“However, the ATP would never suspend Djokovic, Federer, Nadal, or Murray. I don’t think these players manipulate the system, but if they did, it would be suicide for the ATP. The best players are protected. They are too important to be sacrificed.”
Despite his grievances, Koellerer had no desire to return to professional tennis. “I will not return to the tour. But I always wished my little daughter could see me play in a tournament. That was never possible, unfortunately. If it doesn’t happen, I don’t care what happens to this sport. I’m so sick of this damn court,” he said.
Though not for positive reasons, Koellerer left a lasting mark on tennis history.