Henry worked with Willock during his time at the Arsenal academy a couple of years ago.
"When I was with the academy he came along at London Colney at around 16 years old," he said on Sky Sports.
“Although he was still young, as you can see he is still only 18, he was only 16 and he didn't meet his body yet, if I can say. It was kind of weird, he didn't have the conversation yet.
“But he's a good player, he has good technical ability, he can run. He was more of a winger and a 10, Arsene (Wenger) used him in the Europa League as a holding midfielder.
“I'm happy to see him because he's the perfect example of when you don't give up, and you push yourself, you can achieve something.
“Now, it's only his first start in the league so let's not get carried away, but I'm very happy for him because he's worked hard for it.
“Only he can show us what is different about him and if he can stay in that team, that is up to him."