Former world number one Martina Hingis has reversed her decision not to fight anti-doping authorities over a positive cocaine test.
The Swiss tennis star announced her retirement last week after admitting she was under investigation for a positive test for cocaine at Wimbledon on June 29. At the time she indicated that she would not be challenging the result.
But her manager Mario Widmer told BBC Sport on Wednesday: "She will be fighting this, of course. You can be clear about that. The matter is currently with her lawyers."
Speaking at a news conference in Zurich last week, Hingis revealed she had returned a positive result from a routine urine sample taken after losing to Laura Granville in the third round at Wimbledon.
The 27-year-old called the accusations "horrendous" and "monstrous", adding that she had "no desire to spend the next seven years fighting doping officials".
The five-time grand slam champion insisted she was "100 per cent innocent" and that this was backed up by a negative result on a hair test, which can show whether or not someone has taken cocaine.
According to Britain's Daily Telegraph newspaper, Hingis has hired the London-based lawyer Tony Morton-Hooper, who helped former British athlete Diane Modahl overturn a four-year drugs ban.
WTA Tour chief executive Larry Scott told BBC radio: "From what I've read in her statement, and my conversation with her representatives, they are putting forward a case partially based on that.
"There was some suggestion [it was] not a 100 per cent certainty it was her sample that was tested."
But Scott added that it would not be easy for Hingis to prove that she is innocent.
"Once you are found to have a prohibited substance in your system, the burden of proof then shifts to the player," he said.
"If it's in your system you have to prove how it might have got there other than suspicious ways."
Anti-doping officials are astonished by Hingis's decision to go public with the cocaine charge, because she is in the middle of a legal process that will culminate in a personal disciplinary hearing by an independent panel in the near future.
Under the rules of the World Anti-Doping Code, any athlete charged with a drugs offence is guaranteed anonymity until he or she is found guilty. Were she to be cleared by the disciplinary panel, her involvement in a doping case would never be known and her reputation would remain intact.
It is the second time that Hingis, one of the teenage stars of the game in the 1990s, has retired from the professional circuit.
The Swiss star first retired in 2003 due to persistent ankle injury problems, but returned to the circuit in 2006.
swissinfo with agencies
Martina Hingis was born on September 30, 1980. Her mother and father were both accomplished tennis players, ranked 10th and 19th best players in Czechoslovakia, respectively.
Hingis began hitting tennis balls when she was two and entered her first tournament at four.
In 1993, 12-year-old Hingis became the youngest player to win a grand slam junior title: the girls' singles at the French Open.
She made her professional debut in October 1994, two weeks after her 14th birthday. She became the youngest ever world number one in 1997, achieving the ranking at the age of 16 years and 182 days.
Between 1997 and 1999 she won five grand slam tournaments: the Australian Open three times (1997-1999), the US Open (1997) and Wimbledon (1997).
She retired from top-flight tennis in Feburary 2003 because of recurring foot injuries. However, after surgery and long recuperation, she embarked on a successful comeback in January 2006, winning her first major tournament in Rome in June 2006.
In August 2006 she returned to the top ten and climbed to world number 6. In 2007 she won a tournament in Tokyo but pulled out of several competitions due to injury.
Tennis career (1994-2007)
WTA Tour singles titles: 43 (including 5 Grand Slams)
WTA Tour doubles titles: 37 (including 9 Grand Slams)
ITF Women's Circuit singles titles: 2
ITF Women's Circuit doubles titles: 1
Total career prize money: $20.1 million (SFr23.2 million)
Win-loss record singles: 548-133
Win-loss record doubles: 286-54
World Number One for 209 weeks
Youngest top ranked player (1997).
Currently ranked 19th in the world.