Messi's fellow countryman Javier Mascherano is also expected to return for Thursday's 11am session follwing Argentina's disappointing 1-1 draw with Venezuela in Buenos Aires.
Fellow South Americans Luis Suarez and Paulinho are not expected to return until Friday following their international involvement.
That will give the Uruguayan and the Barca new boy just one day to prepare for the club's next La Liga game, something which could cause probelms for the Brazilian as he continues adapting to his new surroundings.