And Danny Care, who is set to partner the 18-year-old at half-back for Quins' season opener against London Irish on Saturday, also admits that Smith has something "special".
Monye even thinks it may not be out of the question that the call from Eddie Jones could happen as soon as the autumn internationals.
"He's a star player. He seems mentally to be the right kind of character, but skills-wise he has a great variety of passing, decent kicking, with good footwork and pace," Monye added.
"I think he will get capped in the next 12 months."
Smith, who only left college in the summer, was drafted into an England training camp earlier this month and Care has had a good look at him in training.
"The kid is special," the England scrum-half told the BBC. "He's incredibly talented and he's going to be a very, very good player.
"He just takes charge of a game effortlessly. So hopefully we can look after him a little bit."
Care says Smith will mentally be able to cope with stepping up a level after impressing for the Twickenham Stoop club in pre-season.
"The great thing about Marcus is it won't go to his head," added Care. "He knows that he's got an awful lot of work to do, but he has a pretty amazing mentor in [former All Blacks and Quins fly-half] Nick Evans, who has just stepped into coaching.
"Everyone is excited about what he can do, but I think it's key people don't push him too hard.
"If I can help in any way, on or off the field, then I will try my best."