Barcelona have confirmed that Javier Mascherano is set to be sidelined for a month through injury, but the club received a boost with the return of Lionel Messi and Ivan Rakitic to training on Wednesday ahead of this weekend's game at Leganes.
Mascherano sustained the injury while on international duty with Argentina.
Barca said in a statement: "During the Argentina-Nigeria friendly match played [on Tuesday], first team player Javier Mascherano had a fibrillar tear in the femoral biceps of his right leg.
"This is confirmed by the tests carried out this morning at the Ciudad Deportiva medical centre. The approximate time of withdrawal is four weeks.
"It should be remembered that Mascherano played the 90 minutes in the defeat of Argentina against Nigeria (2-4).
"[He] has played this season a total of 10 games, six in the league, one in the Copa del Rey, two in the Champions League and one in the Spanish Super Cup."
[BREAKING NEWS] Javier Mascherano has right hamstring injury. More info 👉 https://t.co/jTtnr7jPmU👈 pic.twitter.com/YJTigVrICE
— FC Barcelona (@FCBarcelona) November 15, 2017
Meanwhile, Barca coach Ernesto Valverde welcomed back Messi and Rakitic, with each having been away on international duty.
The pair completed the team's third training session of the week with the rest of the group.
Messi, who has started in all 11 league games for Barca this season and is La Liga's leading goalscorer with 12 goals, played the entirety of Argentina's 1-0 win over Russia at Moscow's Luzhniki Stadium on Saturday.
However, the Argentina captain was given permission by national team coach Jorge Sampaoli to return to Barcelona and rest for a few days and not take part in Tuesday's international friendly against Nigeria.
Rakitic played all 180 minutes of Croatia's playoff against Greece.
Croatia sealed a spot in next year's World Cup after holding Greece to a goalless draw in Piraeus on Sunday for a 4-1 aggregate win.
Barca, four points clear of Valencia at the top of the standings, will take aim at a fourth straight league win against Leganes in Madrid on Saturday.
Information from the Press Association was used in this report.