Spain's Supreme Court on Wednesday upheld a 21-month suspended prison sentence for Barcelona star Lionel Messi in his appeal over three counts of tax fraud, a judicial source confirmed.

However, the Barcelona star's father, Jorge Messi, has seen his sentence reduced from 21 to 15 months for his cooperation in returning some of the defrauded money.

Neither is likely to serve any jail time because, under Spanish law, a tax prison sentence of less than two years can be served under probation.

Barcelona spokesman Josep Vives voiced the club's support for the Messi family.

"The Club reiterates, once again, its full support for Leo Messi, his father Jorge Messi, and his family. This afternoon, FC Barcelona president Josep Maria Bartomeu contacted the player's family to communicate this support. The family was very grateful, not only for today's gesture, but also for the support the player and his family have received from the Club throughout this process. The Club will continue to stand with Leo Messi, his father, and his family."

Messi and his father were first sentenced on July 6 but appealed, with prosecutors eventually asking the Spanish Supreme Court to review the sentences last month.

Prosecutors in last year's case judged that Messi and his father had used tax havens in Belize and Uruguay as well as shell companies in the UK and Switzerland to avoid paying taxes totalling €4.1 million on earnings from image rights between 2007 and 2009.

The five-time World Player of the Year was also ordered to pay a fine of around €2m at the time, while his father was fined €1.5m.

When news of the investigation first broke in the summer of 2013, Jorge Messi, acting on behalf of the Messis, was reported to have paid over €5m in arrears and extra charges -- he is also believed to have paid €10m in taxes due on the image rights income for 2010 and 2011.

Those actions are behind the six-month reduction in his sentence.

Messi said during last year's trial that he signed many documents when he was younger without reading their contents and had visited a notary's office to set up a company to handle his finances without understanding what was going on.

But Mario Maza, the state attorney representing the tax authorities at the trial, said he found it unlikely that Messi knew nothing about the situation.

"It could be that they are inexperienced with tax matters and the law and are not able to set up their own companies, but they are able to understand what paying your taxes means," he said.

Messi is currently in talks about a contract renewal with Barcelona. His current contract is due to expire at the end of next season.

Barcelona have told ESPN FC they are confident he will sign a contract extension, and Spanish radio reported Tuesday that a new deal will be signed at the beginning of next season so that the money is used as part of next year's budget.