Messi stunned the footballing world by informing Barca of his intention to leave last week via an already infamous burofax.
As with Sunday's coronavirus testing for members of Koeman's first-team squad, Messi did not attend because he believes a clause in his contract allowing him to leave on a free transfer is now active, meaning he is no longer a Barcelona player.
This is a version of events disputed by both the club and LaLiga, which issued a statement on Sunday to underline its stance that Messi's huge €700million release clause remains valid within a contract that expires next June.
📍 Ciutat Esportiva— FC Barcelona (@FCBarcelona) August 31, 2020
19 players have trained individually on Camp Tito Vilanova and Pitch 2.@ivanrakitic did not train with the permission of the club.
[+] Info: https://t.co/NZWc8aZXIM pic.twitter.com/5ZkcICDAbH
Koeman is reported to have indicated to Luis Suarez and Arturo Vidal that their futures lie elsewhere, but they both trained among a 19-man group, with a host of senior players away on international duty.
LaLiga announced its fixture schedule for 2020-21 on Monday, with Barcelona given the first two matchweeks off due to their European commitments earlier this month before starting against Villarreal at Camp Nou on September 27.