It seems, it will be difficult for Barcelona in this match, playing away and in the 22nd minute Barcelona defender Cubarsi got a red card. But even so, it seems Benfica also still has enough difficulty to score their first goal in the first half after Barcelona played with only 10 players. But yes,  in the second half it will be very possible for Benfica to score a goal and beat Barcelona in this first leg. But, if Benfica fails to beat Barcelona and the match ends in a draw, then the result will still ensure Barcelona still has a good chance  in the second leg to qualify for the quarter-finals. But so far until the 43th minute, Barcelona is still leading for ball possession, and that is a good effort to not give Benfica a chance to score a goal.