The defender re-joined Southgate’s squad for this week’s crucial Euro play-off against Croatia and has settled straight back into the group almost a year after his last involvement with the Under-21s.
England U21s v Croatia
UEFA Euro U21 Championship
Play-off first leg
5.45pm, Friday 14 October 2014
Molineux, Wolverhampton Wanderers
Live on BT Sport
Call 0871 222 1877 for tickets
Since starring in the 3-0 win over Finland in Milton Keynes for the Under-21s last November, Shaw has featured in a World Cup for England and swapped Southampton for Old Trafford in a record-breaking transfer.
And Southgate revealed his recent call-up to the Under-21s has been a move which all parties have been happy with, as England target qualification for next summer’s Euro Finals in Czech Republic.
"It's great for us [that Shaw is here]," said Southgate. "From his club’s perspective, playing two matches would be good and I know that Louis van Gaal was very positive about it.
"Also, as Louis was a manager of a national team and has spoken so much about the importance of the Under-21s for Holland, we didn’t think we were going to have an issue from the club.
"I just know from the conversation about Luke with Roy [Hodgson] that he [Van Gaal] was very positive about him coming and playing matches for us, first and foremost.
"It is not something where we’ve just thought ‘we’ll make this squad as strong as we possibly can’.
"We are thinking about the individuals all the time and what is the right experience for them.
"For the player, his world has changed a lot since we had him last November but he’s played as many matches for us as the other left-back in this campaign.
"But he’s been brilliant and Roy spoke to him, which I think was important, and I spoke to him before we met up and have had another really good chat with him since we met up."
Shaw arrived at St. George’s Park to meet up with the Three Lions squad on Sunday night, just hours after featuring for United in their 2-1 win over Everton.
After a recovery session on Monday, he has slipped seamlessly back into training with the squad ahead of the first leg with Croatia at Molineux on Friday.
And Southgate believes Shaw's inclusion in the Under-21s squad will be great for both the 19-year-old himself and his squad-mates.
"He’s looking forward to it," added head coach Southgate.
"It’s brilliant for him to have the humility to recognise that [importance of playing for England] and be prepared to do it, it’s also great for us that he’s happy to do it.
"Our group of players can now talk to him about the difference between playing for a club like Southampton, which is a great grounding for any young player, and the expectation level and the different quality when you go to a club like Manchester United.
"They have that informal mixing with him all week, where he can let them know exactly what Di Maria, Falcao and Rooney do in training.
"Jamaal [Lascelles] and Luke [Garbutt] trained with the seniors [on Tuesday] and they thought our training was quick and sharp, but theirs is another level.
"So until players see what the elite level is like and see that pressure they won’t really know it. Luke is going through that process now and it’s great he can pass it on to the rest of the squad."
England play their first leg at Molineux on Friday evening and tickets for the game cost just £10 for adults and £5 for concessions. You can still purchase your ticket for the game by calling 0871 2221877 or by clicking here.
Gareth Southgate speaks to the media ahead of the Croatia game