Barcelona tonight said that Lionel Messi had suffered a bruised left knee in their goalless draw with Benfica.
Messi was taken off on a cart late in the UEFA Champions League match, having collided with goalkeeper Artur Moraes and then twisted awkwardly when trying to curl a shot into the net in the 84th minute.
In an article on their official website, Barcelona said further tests would be required before a timescale could be put on any absence for the Argentinian forward.
He had only come on as a 58th minute substitute with Barcelona already assured of their progress from Group G.
Fans turned up hoping to see Messi match or better Gerd Mueller's record of 85 goals in a calendar year but in the end the night finished on a sour note with the Argentine still a goal behind.
"It doesn't appear too serious as it is a knock to his knee but he will have to have tests now to find out exactly what the situation is," said coach Tito Vilanova.
"He is calm although a little worried as you would expect for a player with an injury who is waiting to know how serious it is.
"I played him for the last 30 minutes to give him a run out and he didn't play just to break the record as if that had been the case then he would have started.
"A player can get injured at any moment and at the end of the day we are Barcelona and we are playing in the Champions League."