The Swede made his home debut on Wednesday night as Arsenal lost 3-2, with Martin Odegaard and Christian Norgaard on the scoresheet for the hosts.
"I think mentally, and understanding what he needs to do, he will be 100% or more," said Arteta regarding Gyokeres' readiness for the Premier League kickoff.
"Because he is so willing and so confident he can deliver straight away, I have no doubts he will be in a really good place.
"We already broke that line today, because I think it was very important for him to start a match and start to have the feeling and the connection with the team.
"He's been with us only a week or so, but I already saw a lot of things and a lot of purpose, especially the way he was attacking in certain spaces.
"So, in general, for a lot of players that haven't played many minutes, we have a lot now that they're going to be ready for Saturday (against Bilbao) in a much better condition."
Quick to settle
Asked how long it will take for Gyokeres to adjust to his new teammates, Arteta also said: "I hope days.
"Every day in training I think he is getting a really good feeling.
"He is building connections outside, which is really important with players that are going to help him to get in the position that he needs to get in.
"His fitness level, he hasn't trained with a team for two months. I think he is on five sessions before today. I think on Saturday he will take another step and be in a better condition."