The Argentine is pushing hard to expedite his exit from Camp Nou and will not attend the medical checks, as well as Ronald Koeman's first training session as coach on Monday.
Messi has stressed that he wants to leave the club, where he has been for nearly two decades, on amicable terms and hopes to reach an agreement over his contract clause.
He believes that the stipulation allowing him to walk away for free which was due to expire in May 2020 should be extended due to the coronavirus situation, and that he should be allowed to leave.
Barcelona, however, remain confident that their legal position is strong and that the clause has expired, meaning he is still under contract for another year and Barca would be able to command a transfer fee for his services.
The club on Saturday informed Messi's representatives via burofax that he is still under contract and that his attendance at the testing on Sunday is mandatory.