Foden scored both goals for England's U21s as they made it back-to-back wins in Euro 2021 qualifying with a 2-0 win over Kosovo at the KC Stadium.
“He's probably not played as well as he can do actually," Boothroyd said. “He's obviously happy with his goals and that's a mark of a good player, always wanting to be better.
“He took his goals really well and the more he plays for us, hopefully it can be a little showcase of what he can do for his club.
“If Phil keeps doing what he's doing and keeps learning. That's the great thing about him, he wants to be better.
“He knows he's not as good as he can be yet and that to me is the most exciting thing about him."