Saka struck the only goal of the night, with Arteta happy the winger is fully fit for preseason.
He said afterwards: "Yeah, we're all very happy with the performance, especially with the attitude, the quality, the determination that we showed throughout the game.
"Obviously to win as well, and yeah, regarding individuals, he was at a really good level, Bukayo is one of them, we have pushed him through the summer as well, to catch up on other things that he had to, to give himself the best chance to explore his qualities, which are better and more highlighted, and with more impact than physically, at the highest level."
On Max Dowman’s appearance, Arteta said: Yes, I'm very happy with all the kids, I think they are able to play at that level, with 15 years old, in my opinion, because of the environment, and the culture that is within the team, and when somebody makes you feel so comfortable, so confident, straight away you can go and do it.
"Obviously it gives you the best chance, you have to have the qualities that this kid has."
Along with Saka, Arteta was also happy seeing Kai Havertz on the pitch after last season's injury frustration.
He added, "Yeah, he's in a very good place, I think the game that he had, I think he was in three or four times, he was completely free, and the ball arrived to him, his workrate, what he offers to the team, it's top. So, he scored against Watford, today he was very close a couple of times as well, overall very happy with him."