Luis Suarez has arrived at world sport's highest court to appeal his ban for biting an opponent at the Football World Cup in Brazil.
The Uruguay and Barcelona forward did not speak with reporters on arriving at the Court of Arbitration for Sport with his lawyers on Friday.
FIFA lawyers also declined comment heading into court for an expected four-hour hearing.
Suarez is trying to persuade a three-member CAS panel to reduce his ban of four months from all football activity and nine Uruguay matches in official competitions.
"We have to have a controlled optimism because we have to respect the panel," Daniel Cravo, lawyer for the Uruguay federation, told reporters.
The court has said it expects to give a ruling next week after FIFA consented to Suarez's request for a fast-track process.
Barcelona start the Spanish league season in two weeks.
FIFA's sanction, which runs through October 25, bars Suarez from training with Barcelona teammates.
Suarez has admitted biting Italy defender Giorgio Chiellini's shoulder during Uruguay's 1-0 win in Natal. Because he has acknowledged the incident, his legal team is unlikely to challenge FIFA on the facts of the case.
"I deeply regret what occurred," Suarez wrote on Twitter June 30, days after FIFA announced the sanctions. "(The) truth is that my colleague Giorgio Chiellini suffered the physical result of a bite in the collision he suffered with me."
Instead, Suarez's lawyers from the Uruguay football association and Barcelona should focus on persuading the three-member CAS panel that the sanctions are too severe.
The international group of football player's unions, FIFPro, has criticised the four-month ban as an infringement of Suarez's right to work.
Suarez has trained alone with a private coach while he is barred by FIFA from Barcelona's stadium and practice grounds.
FIFA did allow Suarez to take a medical to complete his reported (US$126 million) transfer from Liverpool last month on a five-year contract.
Still, Barcelona was denied holding any media events to present its recruit.