The Three Lions secured their place at the Finals in Czech Republic with a play-off victory over Croatia last week.
Southgate’s squad for the two fixtures included defender Luke Shaw, who had started the qualifying campaign with his team before being selected for Roy Hodgson’s seniors and the World Cup earlier this year.
England v Portugal
International U21 Match
7.45pm, Thursday 13 November 2014
Turf Moor, Burnley FC
Live on BT Sport
With Under-21s’ top scorer Saido Berahino catching the eye with his form for West Bromwich Albion, there are calls for the striker to be the latest of Southgate’s youngsters to make the step into Hodgson’s group.
But Southgate believes the approach taken to moving players through the England development age groups can be replicated between his squad and Hodgson’s group.
"It’s quite helpful from Under-21s down that I oversee all the teams, without coaching, so it’s important that we have the conversations and we debate intently about if we’re going to move anybody up or down," revealed the former Aston Villa and Crystal Palace player.
"More and more now, we won’t do that at all before U18 level as we don’t want to push 15 or 16-year-olds up too early.
"The U17s won the Euros last year and we had a long debate about who we would move into the U19s and we’ve only put three up at this stage.
"It’s the same with the Under-21s and the seniors but with all of those other age groups. We still reserve the right to move back down.
"With the nature of the seniors, you can move up but you won’t necessarily always play.
Watch England Under-21 head coach Gareth Southgate's message to his squad after they qualified for the Euro Finals in Croatia
"If you find yourself not playing for a period of time with the seniors, how do you get the progression and learning opportunities that are required?
"It shouldn’t be seen as players coming ‘back down’ as though that’s some sort of punishment or not part of their development - we’ve got to make that movement between the squads more fluid."
The Under-21s will be back in action in November when they face Portugal at Burnley’s Turf Moor home, where Southgate’s planning for next summer will really commence.
And regardless of speculation over who might be the next member of his squad to make it into Hodgson’s group, the head coach is open to the prospect of those players returning to the Under-21s as focus turns to June 2015.
"These are still young players and at a club level, you might play with the first team and then be back in the juniors a couple of weeks later and that’s part of the process," he explained.
"I think because we haven’t done it so often in the past, it’s viewed slightly negatively at times but it is something that we’ve done through the season and we feel it’s the right thing to do.
"It’s a good challenge for them, they’re still young players. I’m in the fortunate position of having played in a World Cup myself so I understand from a player’s perspective but also, as young players, there’s a long way to go.
"It’s the same with Lewis Baker who came up from the U20s squad last time, because we want the U20s programme to be valued and he captained them last time around.
Watch highlights from the game as England Under-21s qualified for the Euro Finals
"So after losing [Nathaniel] Chalobah and [James] Ward-Prowse, we felt it was reward for Lewis and also a sign for the others in that group that there’s a chance to progress.
"Roy and myself are very much on the same page with this. We want to have a real crack at this competition [Under-21s Euros] and we think in two or four years, it will only benefit the group who have been on it.
"But some of these lads will have a lot of football with their clubs during the season so we’ve got to see what’s right for each individual.
"We have discussed this right the way through and generally speaking the seniors have taken priority because they have to come first."