Adrian Mutu has appealed against the Premier League's decision to allow Chelsea to seek compensation following his positive drugs test.
Mutu signed for Juventus in January
Mutu was sacked in October after a positive cocaine test and was handed a seven-month worldwide football ban.
The disgraced Romanian striker, 26, has since joined Juventus and the Blues are hoping to recover £8m of the £15.8m they paid to Parma in August 2003.
But Mutu has now taken the matter to the Court of Arbitration for Sport.
A CAS statement said: "Mutu requests CAS to reverse the determination of the Appeals Committee and to rule that the facts of this case do not give rise to a 'unilateral breach of the contract without just cause' by the player."
Chelsea had been given the green light by the Premier League appeals committee to seek compensation, arguing that Mutu broke his contract by persistent misconduct.
At the time of the Premier League ruling Chelsea issued a statement which said: "We are obviously pleased that the Appeals Committee has vindicated the club's position and opened the door for a compensation claim and sporting sanctions before Fifa's Dispute Resolution Chamber.
"Chelsea will continue to pursue the case vigorously as the principle is an important one."
Although Mutu is Chelsea's opponent in the case, if any damages were awarded, they would be payable by Juventus.
The matter will now be referred to Fifa, and it is possible Chelsea could even take the matter to a civil court.
Mutu was dismissed last October for gross misconduct after the positive test.
Following a Football Association hearing in November, he was fined £20,000 and suspended from all football for seven months.
Chelsea were anxious to block Mutu signing for another club on a free transfer at the end of his suspension but he signed for Juventus in February and has been training for them since.
A statement from the Premier League read: "The appeals committee concluded that the conduct of the player in taking banned drugs was gross misconduct which entitled the club to treat the player's contract as at an end and amounted to a unilateral breach without just cause or sporting just cause.
"The club is therefore entitled to proceed to seek compensation and sporting sanctions from the dispute resolution chamber (DRC) of Fifa."