Now they take on the Portuguese giants at the Emirates Stadium on Tuesday, needing a two-goal win to go through.
If you see the stats it is the reality," said Arteta to reporters ahead of the game.
Let's try to change it. How? Prepare the best possible way. Make a lot of right decisions and then be brave. You cannot wait in these situations, you have to go and make things happen. That's the approach (against Porto).
Knockout games are different. You see it when we went out in the Europa League after going ahead and losing in the last minute, and against Sporting on penalties. The details and the margins are so small. That is a huge part of these knockout games." Porto prevented Arsenal registering a shot on target for the first time in two years in the first leg won by Galeno's late wonder strike.
We're certainly going to have to tweak a few things to generate much more than we did," added the Spaniard.
It's the level of the Champions League. You're facing top teams. The fact that there are two games plays in your mind and we have to be better."