Barcelona forward Lionel Messi is set to undergo tests on Wednesday after sustaining a hamstring injury during the Champions League quarter-final match at Paris Saint-Germain.
The club also announced that Javier Mascherano is likely to be out for around six weeks after suffering a knee problem in the game, which ended in a 2-2 draw.
Messi, 25, appeared to pick up his injury after taking a strike on goal near the end of the first half, shortly after he had netted the opening goal. He was withdrawn at half-time and replaced by Cesc Fabregas.
A message on the club's official Twitter feed read: "Messi sustained an injury to his right hamstring. He will undergo further tests on Wednesday to determine the extent of the injury."
Reports suggest the forward could be out for around three weeks.
Mascherano also had to be substituted late on and would appear to have no prospect of featuring in the return leg at the Camp Nou.
With Carles Puyol not expected to be available after undergoing knee surgery last month, Marc Bartra, who replaced Mascherano at the Parc des Princes, could partner Gerard Pique in next week's match.