The Gunners won the first-leg 3-2, through efforts from Ben White, Viktor Gyokeres and Martin Zubimendi.
Arteta said: "I think we all need everybody to be at their best when we need them, and Ben certainly has stepped up tonight. Again, once more, I'm used to it, because he's done it every time that he's been with us, but I think individually we have some big performances tonight."
Indeed, on Gyokeres, he continued: "I think he had a great game, he was a real threat constantly, really supporting the team in the way that we actually needed today, he scored the goal and he could have scored another one."
Arteta also enjoyed Zubimendi's goal, which proved the matchwinner on the night.
"Unbelievable, it was a beautiful goal to watch," the manager said. "The composure that Zubi shows, again, in and around the box, he was top class, and a goal that is very important for us."
"I'm very happy with the performance, first of all, and then the victory. It's a really tough place to come, they are top side, top individuals, and I think the team made another step in the manner, the determination that we want to play.
"It feels at 1-3 and the dominance that we had in the game, and the two massive chances that we missed to put the game into a very different position, but at the end, one goal is not enough."