Lionel Messi trained alone on Saturday as Argentina continued its preparations for the team's Copa America Centenario opener against Chile.

Albiceleste captain Messi had to be substituted after sustaining a knock to his back during his country's friendly against Honduras last week, sparking fears he may not be fit in time for Monday's re-run of the 2015 Copa final in Santa Clara.

Messi is back with Gerardo Martino's squad in California after returning to Barcelona to give evidence in a tax fraud trial against him and his father in midweek, but the Ballon d'Or holder was unable to train with his teammates.

A statement on the Argentine Football Association's official website read: "Lionel Messi and Lucas Biglia trained separately, while Javier Pastore and Ezequiel Lavezzi participated in the group play with a ball and then practiced apart."

It remains to be seen whether Messi will take part in Sunday's final training session before the Chile match.