While Croatia possess arguably the best central midfield pairing in the tournament in Real Madrid's Luka Modric and Barcelona's Ivan Rakitic, Southgate's language does not indicate he is about to bring in Eric Dier as an additional defensive midfielder alongside Jordan Henderson.
Defender Vrsaljko was also instrumental, clearing a shot off the line in the first half of extra time as well as setting up Perisic's equaliser.
The victory is historic for Croatia, the second smallest nation to make the World Cup final after Uruguay, but it's no fluke.
England has shown that fielding a team young enough to forget the mistakes of the past can be incredibly useful in building confidence - especially when that team is led by a former player from those years of mediocrity. It shows we can be up here, that we can win knockout games, can get to semi-finals and the next step is to go one step further. "God willing, we will be world champions".
The Inter Milan man's effort off the woodwork was the closest either side came to taking the lead before the 90 minutes were up, meaning England faced a second period of extra time at Russian Federation 2018 - with Croatia undertaking a third consecutive additional 30 minutes.
Trippier's curling fifth-minute free-kick was his first worldwide goal, a prominent example of the quality of his delivery that has given rise to the "Bury Beckham" moniker because he was born in Bury near Manchester.
It was their 12th goal of the tournament and ninth from a set-piece, but they should have added more from open play as they reveled in the space they were being given and looked completely in command. Harry Kane struck the post, Raheem Sterling and Jesse Lingard spurned good chances, and Croatia somehow held on to go in just one behind at the interval. Kieran Trippier's excellent free-kick from the edge of the Croatia penalty area gave Gareth Southgate's side the lead early in the game.
Croatia emerged for the second half stronger and equalised on 68 minutes when Ivan Perisic got ahead of Kyle Walker to flick home a finish on the volley.
Perisic should have added another when given a great shooting chance but he cannoned the ball against a post as England's defense began to lose shape. They topped an extremely hard group that included perennial title contenders Argentina, Iceland and Nigeria. Including extra-time, Dalic's side has now scored at least two goals in five of their last six games.
"This is a miracle".
"We were like lions out there tonight and we will be the same in the final". "There's a lot we could have done better".
England had no answer - neither on the field as their passing game was replaced by hasty clearances and long balls forward nor on the bench as Southgate was unable to make the switches that might have changed the game.
"I am immensely proud by the way the players have played and we can see by the reaction of the supporters, they felt the same".
"I think it's our year this time".