Spain's Supreme Court on Thursday started reviewing a 21-month jail sentence handed to Lionel Messi and his father for tax fraud after the Barcelona star lodged an appeal, a spokesman said.
But even if the sentence is maintained, neither Messi nor his father are likely to spend time behind bars, as is common in Spain for first offences for non-violent crimes carrying a sentence of less than two years.
A spokesman for the Supreme Court said the case was being examined by five magistrates, a process that could last several days.
News of the review comes just days before Barcelona face Real Madrid in El Clasico on Sunday with their Spanish league title at stake.
Argentina international Messi and father Jorge Horacio Messi were found guilty last July of using companies in Belize, Britain, Switzerland and Uruguay to avoid paying taxes on 4.16 million euros ($4.5 million) of Messi's income earned from his image rights from 2007-09.
Messi has always maintained he knew nothing about how his wealth was managed and trusted his father with his finances. His lawyers appealed the sentence.
Messi's tax fraud trial took place in Barcelona last June against a backdrop of simmering voter anger over steep cuts to health and social spending, as the government struggles to bring Spain's public deficit down.
The court argued in its ruling that the 29-year-old five-time world player of the year "decided to remain in ignorance" about how his finances were managed.
It added that if the player was not punished, "ordinary" citizens could conclude that it was better to "not show interest" in their tax obligations.
Messi was also fined 2.09 million euros and his father 1.6 million euros.