The 48-year-old has handed maiden call-ups to Jadon Sancho, Mason Mount and James Maddison.
"Very often we hold youngsters back a bit too much", said Southgate, who previously coached England's under-21 team.
"He's a player that we know has good technical quality, is grasping the tactical side of the game - I was interested to read his interviews this morning on that - so it's a good opportunity for him to come in".
Under Southgate, England had the second-youngest squad at the World Cup and the team had an energy and enthusiasm not seen in the national team in years.
The new contract is understood to include a significant pay rise, which will mean Southgate earns 50 per cent more than he did for guiding England to the semi-finals of the 2018 World Cup.
Southgate marks new deal with bold selections for England’s Nations League tasks
"I'm really pleased we are able to have that stability and it's important that we connect all the junior teams to that", Southgate told reporters.
"There is an opportunity there", he added, regarding the injured players. We have some injuries in midfield, so there's an opportunity there.
"But we think they are performing well with their clubs, they're confident players. Experiencing at first hand how the nation united behind the team this summer was something special and it will be great to see how far this young squad can go in the years to come".
In fact he has created more goals than any other player in Europe's five major leagues this season (5). He recently signed a new contract with the German club. "He's started two Champions League games for Dortmund and he's had a really big impact from the bench in their league matches so that's been a really fearless decision from him to go and seek his opportunity".
Since his move from Norwich City for £20 million, the 21-year-old has been in fine form for the Foxes, having bagged three goals and two assists for the side so far.
Borussia Dortmund have extended the contract with England's U-19 global Jadon Sancho ahead of schedule, the "BVB" confirmed in an official statement on Wednesday. The selection of Sancho and Mount, as well as set-piece specialist Maddison, is Southgate's way of confronting that problem.
Gareth Southgate says the "big call" to select Borussia Dortmund teenager Jadon Sancho aligns with England's current philosophy.