Mascherano suffered the injury during Argentina's friendly loss vs. Nigeria.
Barcelona defender Javier Mascherano is expected to miss four weeks of action after suffering a hamstring injury in his right leg while away on international duty with Argentina this month.
Mascherano sustained the problem during his country's friendly against Nigeria in the Russian city of Krasnodar on Tuesday night.
The 33-year-old underwent tests at Barcelona facilities upon arriving back in Spain the following day, with the club releasing a short statement on the matter on Wednesday afternoon.
The club estimates that Mascherano, a four-time La Liga and two-time Champions League winner, will now have to spend around a month on the sidelines.
No longer a regular starter as a result of Samuel Umtiti's arrival in 2016, he has played six times in La Liga so far this season, as well as twice in the Champions League and captaining the side in the Copa del Rey. His absence and the impact on squad depth will still come as a blow..
Barça have a busy few weeks coming up and Mascherano could be ruled out of as many as seven games depending on how his recovery progresses.
He stands to miss La Liga fixtures against Leganes, Valencia, Celta Vigo and Villarreal, as well as Champions League games against Juventus and Sporting CP, and the Copa del Rey return against Murcia. Barcelona are later due to face Real Madrid on 23rd December.