Kai Havertz finished a superb pass from Gabriel Martinelli for the 1-0 quarterfinal first-leg win after the pair came on in the second-half.
"It's been the story of the season, how important the finishers have been for us, to achieve what we want. And today, all of them - Gabi came on and made a huge impact; Kai the same; Max (Dowman) the same. So we really need that, and we're really happy with that."
“It’s very difficult to win away from home in the Champions League,” he added, “and certainly against a team that have won 16 games in a row at home, so that tells you what we've done.
“We had moments where we were very, very dominant, and we had our chances, we lacked certain threat in and around the box - we needed to be more efficient and crisper with our last pass, and as well we needed David twice to make a save to help us to win."
Despite the advantage, Arteta warned nothing is yet won.
He added: "One hundred percent, they know that, they know how tough it's going to be now at Emirates Stadium, and we'll be fully ready for that.
“The supporters were exceptional again, thank you so much for following all the way here, and being with the team. We're very happy to give them the victory.”