England face Croatia and Spain in UEFA Nations League matches later this month, and Gareth Southgate named three uncapped youngsters in his squad.
Borussia Dortmund's Jadon Sancho, Leicester's James Maddison and Derby's Mason Mount all earned their first call-ups in the absense of Dele Alli, Jesse Lingard, Adam Lallana and Ruben Loftus-Cheek who are all injured or lacking fitness.
Boothroyd remarked: "It's probably a little early for the boys but what we have seen is a strategy evolving that if players do get injured or come out of the first team, Gareth immediately looks at the U21s.
"He doesn't look at players who might be ageing or just coming to do one job. He is looking to the future and it should be applauded, it's another brave decision.
"It puts them in the spotlight and in the environment to thrive in the seniors but, because we're all joined up, if the other guys come back and Gareth decides not to pick them [the youngsters], they'll come back down to me.
"Then they have got to fight for their place in the U21s squad then because that's not bad either."
"Because of the injuries the team has got it just gives them an opportunity. Jadon has done really well, he has come in and created goals and scored, and Mason has been outstanding at Derby.
"The same with James, he had his season in the Championship, got his move, and has done really well so deserves looking at.
"In a different era it would take 100 appearances in the top flight before they got a cap but we live in different times.