Due to Spanish law, Messi will not serve time, as he is a first-time offender and it is a non-violent crime.
Messi, 29, a five-time world player of the year victor, was also fined 2.09 million euros while his father was fined 1.6 million euros.
Ronaldo and Messi are the only football players in Forbes' top ten, which also includes two European tennis players, Roger Federer and Novak Djokovic.
Tebas says, "Of course I fear that (Messi) could leave, but the only thing I can tell him is that from LaLiga we believe he isn't guilty".
Barcelona have launched a campaign in support of Lionel Messi and his father Jorge after the Argentine pair were sentenced to prison terms this week over tax fraud.
Barcelona issued a statement to "give all its support to Leo Messi and his father".
He said his father had control over his financial affairs, but the court said on Wednesday that this was not enough to avoid charges and Messi's "ignorance" did not remove responsibility.
In a post on his Twitter account, Bartomeu wrote: "Leo, those who attack you are attacking Barca and its history".
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Messi shocked the world by calling it quits from global football after his team failed to pass the final hurdle in Copa America 2016 against Chile.
Messi, 29, joined the club's academy in 2000, aged 13, and his family joined him in Spain soon after.
With Barcelona, in contrast, Messi has won four Champions League titles, three Club World Cup trophies and eight Spanish league titles.