The first-team squad are currently in Germany, where they have been based for the past week.
They are preparing for a pre-season friendly game against Salzburg on Wednesday.
Summer signing Sergio Aguero was expected to start preseason on Monday, but returned a few days early and has been working alone at the club’s training base since Friday.
Brazil defender, Emerson Royal, also underwent COVID-19 and medical checks on Monday ahead of returning to training this week.
Messi was also due back in today, but ESPN reports the club and the player have decided to delay his start date.
As a free agent, the 34-year-old would be allowed to use the club’s facilities, as long as adequate insurance is in place, but the decision has been made to wait until his new deal is signed.
