Mariano Puerta's ban for failing a doping test after the 2005 French Open has been cut from eight years to two.
Puerta lost to Rafael Nadal in the 2005 French Open final
The Argentine, who served a nine-month ban in 2003 for taking banned anabolic steroid clenbuterol, tested positive again for etilefrine in June 2005.
An International Tennis Federation tribunal in December imposed an eight-year ban from 5 June, 2005.
But the Court of Arbitration for Sport has reduced this to two years, allowing Puerta, 27, to play from 5 June, 2007.
When it was announced on 21 December, Puerta's ban was the longest in tennis history at eight years.
Puerta had claimed the drug entered his body just before the 2005 final after he inadvertently used a glass that had previously been used by his wife, who takes a treatment containing etilefrine.
The ITF panel concluded at the time that Puerta had failed to exercise "utmost caution" but added that "his fault was not significant".
A ban of eight years was still imposed, however, as it was in accordance with the World Anti-Doping Code's sanction regarding a second offence.
Puerta described the eight-year ban as "extraordinary" and appealed to Cas, which stated in its ruling on Wednesday that the ITF and Wada "did not provide for the case of an athlete guilty of two non-significant offences".
As a result, Cas said it would fill this gap "by imposing on the player a sanction proportionate to the faults committed.
"Therefore, the player has been disqualified from the French Open 2005 and suspended for a period of two years starting on 5 June 2005 until 4 June 2007."