The 20-year-old joined Spurs from Sporting Lisbon in a £4m deal earlier this summer and has already impressed with his pre-season performances at White Hart Lane.
And after coming through the youth ranks of the Portuguese club after moving there with his family as a child, Dier now will be looking to make a name for himself in the Premier League.
"I know Eric was keen to come back to England, he had a difficult season last year when he didn’t get a lot of first team football in Lisbon," revealed Southgate, whose squad face their final two Euro qualifiers in Lithuania and Moldova next month.
"He’s a young centre-back who will mature but he plays in a position which takes time to develop so it’s an interesting move for him to test himself over here."
Cheltenham-born Dier, who has also played for England at U18, U19 and U20 level, was one of very few English players plying their trade overseas and with one of the biggest clubs in Portugal, which is something that Southgate was always encouraged by.
But when Dier was presented with the chance to join Spurs, and join his family back in London, it was an opportunity he couldn’t turn down.
"We monitored him very closely when he was in Lisbon and I didn’t mind the fact he was over there," added Southgate.
"In fact, I thought it was a real positive for us to have a player playing abroad.
"To try and get into the first team at Spurs will be a big challenge for him, but he might feel that it helps his cause because it’s easier for us to get to see him."
Southgate will be naming his squad for the trip to Lithuania and Moldova on Thursday 28 August.