Saka had a 13th minute penalty saved, but was still impressive on Wednesday night as the Gunners won 2-1 to reach the semifinals 5-1 on aggregate. The England international struck first on the night in the second-half.
Arteta said: "I can go on and on with individuals and a lot of different cases, I will answer in that same way.
"With Bukayo, he stepped up, he didn't score, obviously, that could be a turning point emotionally in the game because it gives him a lot of belief.
"But then the way he handled the situation, the way he played afterwards, and the personality that he showed at his age. It's the first time he's played in this stadium, it's incredible."
Declan Rice was again superb in midfield for the Gunners and Arteta described the performance as "immense".
He added: "He was decisive today in a different way, I think it was immense. His presence, the power that he showed, how composed he was, with or without the ball, I think he led the team in many moments and turns the game in our favour.
"I think that's why we need players at his level to step up and have a big contribution, and he certainly has done that."