Mikel Merino jumped from the bench to score both goals late on for the win in today's early kickoff.
Arteta said: "We knew it was going to be tough. The first 20 minutes, we were too sloppy. It opened up the game a little bit. We didn't have a real threat and we weren't playing with enough urgency. We were much sharper in the second half. Mikel could give us something with Trossard off the left."
On Merino's attacking qualities, he said: "He certainly has. He has a sense of danger and great timing in the box. We were on the verge of about to get to a different level of anxiety. We were composed, scored two brilliant goals and could have scored one or two more."
On Ethan Nwaneri and Myles Lewis-Skelly: "Physically they are built in a really special way already. Emotionally and mentally, how composed they are, and how they make decisions on the pitch are really impressive so let them go.
"That's what we want. Let's go day by day and take a lot of positives from the second half but also know the first half wasn't good enough to win games."