The French Under-21 international made his first start for the Gunners on Sunday as they were beaten 2-1 by Galatasaray.
"He's a strong boy," Walcott told the club's official website. "He's only had a couple of training sessions with us. I've only trained with him a couple of times.
"He's a nice lad and I think he'll do very well for us. There's a lot of competition for that position."
Arsenal play their final pre-season fixture on Saturday when they face Manchester City in Helsinki.