It is about a muscle tear in the left thigh, the club announces in a statement on Sunday.
According to Spanish media, the 36-year-old may be out for three weeks, which means he risks missing Saturday's cup final against arch-rival Real Madrid in Sevilla and the two semi-final matches in the Champions League against Inter (April 30 and May 6) as well as two league matches.
The Pole has scored 40 goals this season – all competitions included – and is thereby Barcelona's top scorer.
He was substituted due to injury in the 78th minute in Saturday's home game against Celta Vigo in La Liga football. Barcelona then turned a 1–3 deficit into a 4–3 victory. The decisive goal was scored by Raphinha on a penalty in the eighth added minute.
Barcelona, with six matches left to play, still tops the La Liga table ahead of the reigning champion Real Madrid.
