Kepa joined Arsenal in the summer from Chelsea and has largely acted as cover for David Raya.
The Spain international is set to start in tonight's Carabao Cup tie with Brighton and Arteta said: "David (Raya) has been incredibly good for us in the last few years and Kepa knew that when he came in, but he's ready to compete.
"If I have to highlight behaviours in that dressing room and culture, probably I would mention him as number one, because again, he's come into a different environment after winning everything in football, almost, being in the national team, Chelsea, Real Madrid, big, big clubs and he comes here and every single day he's behaving like tomorrow's training session is the most important one in his life.
"He will have his chances to play, he's in a really good place, and if he plays tomorrow, I'm sure he will be really, really good. I think Kepa has raised the level, he has created a true great environment for everybody to shine and I think that's down to him."