PHOTOS: The dope cheats who shocked tennis!

Tennis is facing its worst times in terms of dope cheats.

Serbian former World No 12 Viktor Troicki was slapped an 18-month ban by the International Tennis Federation for refusing to provide a blood sample at this year's Monte Carlo Masters.

- Croatian tennis player Cilic fails drug test?

- Troicki pleads innocence, to appeal to CAS against ban

In his defence, Troicki maintained that he was misled by a doping control officer in Monte Carlo.

Meanwhile, world No 15 Marin Cilic tested positive at the Munich Open three months ago.

Cilic is perhaps the sport’s highest-profile case since Frenchman Richard Gasquet was handed a 12-month ban in 2009 after traces of cocaine were found in his system. He was later cleared by the Court of Arbitration for Sport, which accepted that he accidentally ingested the banned substance after kissing a woman in a Miami nightclub.

With the menace of doping returning to haunt tennis, Rediff.com takes a look at players who tested positive for use of banned substances over the years.

Martina Hingis

This tennis wonder girl was not too lucky in her second innings.

She tested positive for cocaine during Wimbledon in 2007, her comeback year.

She was banned for two years and quit the sport, but made a return to playing doubles this year.

The 'Swiss Miss' has repeatedly protested her innocence.

Jennifer Capriati

She gave hope to young American girls before the era of the Williams sisters. The American won an Olympic gold medal at the 1992 Barcelona Games at the tender age of 16.

But soon, it seems, her attention was diverted. She was arrested for possession of marijuana.

But the fighter in her did not give up easily. She rebuilt her career and went on to win three Grand Slam singles titles.

Andre Agassi

Andre Agassi's admission in his autobiography 'Open', that he lied to tennis authorities about the use of addictive stimulant crystal methamphetamine to escape a ban shocked the world.

The eight-time Grand Slam winner said he wanted to share "my bad decisions which, in a few instances, nearly ended in catastrophe".

Agassi admitted he used the drug with an ex-assistant in 1997.

Richard Gasquet

Richard Gasquet escaped narrowly. The French player was suspended in May this year, pending an investigation into a failed drugs test he gave at the Miami Masters in March.

However, he was cleared of wrongdoing after explaining the drug had entered his system after kissing an unidentified woman at a nightclub, and returned to action.

Greg Rusedski

Rusedski, then Britain's No 2, tested positive for nandrolone in 2003.

The news was revealed in January 2004 and two months later Rusedski was cleared after successfully arguing that any excess levels in his system must have been mistakenly given to him by trainers.

Mariano Puerta

The former World No 9 was twice banned from the sport due for drug offences.

In 2003 he was ordered off the Tour for two years at Vina del Mar, later reduced to nine months, after testing positive for clenbuterol, which he stressed had been administered to him by his doctor to combat asthma.

In 2005, after reaching the French Open final, the Argentinian was banned for eight years, the longest in tennis history at that time, for the use of the cardiac stimulant, etilefrine. Later it was reduced to two years.

Puerta claimed it had entered him after using a glass used by his wife, who was on medication.