Michel Platini has begun his appeal at the Court of Arbitration for Sport against a six-year ban by FIFA over a $2 million payment approved by Sepp Blatter.

The UEFA president did not speak with reporters Friday after arriving for an 8 a.m. (0600 GMT) closed-door hearing expected to last at least eight hours.

A verdict could come as early as Monday, when UEFA gathers in Budapest, Hungary, ahead of an annual congress of 54 soccer federations who have been without their leader for seven months.

"Hopefully it will be early next week, maybe a little later," CAS secretary general Matthieu Reeb said. "The CAS tribunal will adapt itself to the needs of the parties."

The three-member CAS panel is judging Platini's case again and has the authority to impose a life ban for corruption.

Previously, FIFA's ethics and appeals committees ruled out bribery as a factor and found Platini and Blatter guilty of charges including conflict of interest and disloyalty.

Blatter, the former FIFA president, arrived at 10:30 a.m. to serve as a witness. Blatter employed Platini as a presidential adviser from 1999-2002.

"I accepted this task. I'm on good form and I'm happy to be a witness in this matter," Blatter said outside the court.

Platini and his former mentor deny wrongdoing, and claim they had a verbal contract for the additional money. FIFA eventually paid Platini three months before Blatter was re-elected as president in 2011.

Both are effectively the star witness in each other's appeal case, after they were heard on back-to-back days by the two earlier FIFA tribunals.

This time, Blatter's appeal against his six-year ban will be heard at a later date, and by a separate CAS panel of judges.

It is probable, and unusual in sports law, that Platini's verdict will be announced before a hearing is held for Blatter, despite their cases involving much of the same evidence.

Platini has shown more urgency to go to CAS as he and UEFA seek clarity before the European Championship kicks off on June 10. Platini hopes to clear his name to oversee the tournament, being played in his native France for the first time since 1984 when he captained the host nation to victory.

UEFA's priorities include organizing a presidential election, possibly in Paris in June, to replace Platini if he remains banned.

One of the potential candidates to succeed Platini was among the witnesses Friday. UEFA and FIFA vice president Angel Maria Villar of Spain declined to speak with reporters before and after his 90-minute session in the court.

A third witness is Jacques Lambert, the Euro 2016 tournament director and a longtime friend of Platini. Lambert and Platini led the 1998 World Cup organizing operation in France before the former France great was employed by FIFA.

Long seen as Blatter's heir apparent, Platini's chances of becoming FIFA president was ended by the payment, which became public knowledge last September when Swiss federal prosecutors opened criminal proceedings against Blatter for suspected mismanagement.

Blatter was replaced as FIFA president two months ago by Gianni Infantino, Platini's long-time right-hand man at UEFA.

Six weeks before Euro 2016 kicks off, UEFA has no working president and an interim secretary general.

CAS appointed Luigi Fumagelli of Italy to chair the panel judging Platini. Fumagelli was a member of the panel which upheld a four-month ban for Barcelona forward Luis Suarez for biting an Italy defender when playing for Uruguay at the 2014 World Cup.

Platini's legal team chose Jan Paulsson of France from the list of CAS-approved judges, and FIFA picked Bernard Hanotiau of Belgium.