"(He suffers) a small tear in his left thigh muscle. The injury is in a risky area and it will take four to six weeks to recover from," Barca's website said on Monday.

The Argentinean international scored in his side's 3-1 victory over Real Zaragoza over the weekend but sustained the injury in the dying seconds.

He joined compatriot Messi, who was confirmed earlier this week out of action for three months with a foot injury.

Barcelona top scorer in the last two years Eto'o is also out for four months with knee troubles, leaving manager Frank Rijkaard facing a shortage of players in the attacking line.

The Dutch coach now has only one striker in Eidur Gudjohnsen, supported by attacking midfielders Ronaldinho, Ludovic Giuly and Santiago Ezquerro.

Barcelona may face troubles in their domestic title defending campaign although they are placed on the top of the table with 23 points, one and two points ahead of challengers Sevilla and Real Madrid respectively.

They will also have tough time in their remaining matches in the Champions League where they are third in Group A with five points from four games.

Leaders Chelsea have ten while second-placed Werder Bremen collected seven points.