Wenger praised Ryo's direct movement and attitude and is pleased to see the 20-year-old nearing a return to full fitness, after he suffered an ankle injury on loan at Wigan Athletic last season.
"I was personally impressed by his pace, his movement off the ball, his desire to go forward and take on defenders and as well by his fantastic attitude," Wenger told arsenal.com.
"I was convinced in the first session that Ryo deserved a chance. He has been a bit unlucky because he is not completely 100 per cent fit yet because he has been out with a long injury.
"He had a little knock back at the start of training but now it will take him two or three weeks maximum to be back to his best physically because he has done great work to repair. That's why he is at Arsenal."