Mourinho has been accused by prosecutors of defrauding Spain of 3.3m euros (£2.9m) in taxes while he was Real Madrid coach from 2011 to 2012.
However, the waters were further muddied on Friday morning when prosecutors said they were not against Messi's 21-month sentence being converted into a €250,000 fine - €400 for every day of the sentence - on top of the €2m fine Messi has already paid.
In Spain, sentences less than two years are normally suspended unless the individual has a prior conviction. Now, the admission of the two counts of fraud in 2012 and 2013 will see him pay an additional fine of nearly 780,000 euros.
"It is a personal decision and if a person really wants something to happen then it will end up happening, but I see it as unlikely", added Figo, who played at the Bernabeu between 2000 and 2005.
He will plead guilty to two charges of fraud relating to image rights during his time at Real Madrid.
Ronaldo has not spoken to the media since reports emerged in Portugal of his desire to quit Madrid over a perceived lack of support from the club after Spanish authorities opened an investigation into allegations of tax fraud against the former Manchester United forward.
According to The Irish Times, Di Maria had transferred his image rights to the Panama-based Sunpex Corporation, before Sunpex ceded his rights to the Dublin companies Multisports & Image Management (MIM) and Polaris Sports.
In March, a day after being summoned to answer a judge's questions regarding the fraud investigation, Di Maria paid 1.45 million euros ($1.6 million) to Spain's Tax Office.
Mourinho left Real Madrid in 2013 to manage English club Chelsea for a second spell before signing with Manchester United in 2016.
Neymar and Cristiano Ronaldo play for the biggest rivals in La Liga, but it has now been reported that the FC Barcelona superstar recently sent a WhatsApp message to his Real Madrid counterpart.
Di Maria initially agreed in February of this year to pay 1.45 million euros.
The soccer star is due to appear in court on July 31.