Puyol fell badly in the second half to damage his arm, when his side was already 2-0 ahead thanks to goals from Alexis Sanchez and Cesc Fabrigas.

It was tremendous bad luck for a player who has suffered two bad knee injuries in recent months and whose return to action after a rapid recovery from a knee ligament injury was the big surprise in the starting 11 presented by Barca coach Villanova.

There was no place for Andres Iniesta in the starting lineup, however, as Vilanova decided to retain Xavi Hernandez in his side, despite the proximity of his side's huge match at home to Real Madrid next Sunday.

The game was barely five minutes old before Barca took the lead. Leo Messi beat his man on the left and his driven cross was prodded home by Alexis Sanchez from close range. Alexis has been criticized for his poor early season form and the goal will have given him a confidence boost.

Barca were controlling the ball and just before the half hour Alexis had another chance, although a combination of rapid defense and the good work of Benfica goalkeeper Artur Moraes stopped him getting a shot on goal.

The half ended with Pedro Rodruguez crossing for Messi, who was unable to hit the target with his shot.

In the second period, Barcelona again continued to move the ball around with ease, but they were suffering from set pieces in their penalty area.

Nevertheless, Cesc Fabriagas doubled the lead less than 10 minutes into the second half with a left foot shot from inside the Benfica penalty area.

Messi almost doubled Barca's lead with a powerful header, which was well saved by Artur, before Barca suffered a massive setback when Puyol fell badly in challenging for a ball. TV replays showed how his arm was bent behind him and the defender was carried from the field in agony as the Benfica fans stood up to applaud in respect.

Puyol's injury is a huge blow for Barca ahead of the Classico against Real Madrid this weekend, although it may be compensated by the fact Iniesta also enjoyed minutes as a substitute in the second half.

Barca ended the game with 10 men after Sergio Busquets was shown a direct red card, although the reason for his sending off was by no means clear.