The Croats needed extra-time and penalties for the second successive knockout game, beating Russian Federation last time, so it wouldn't be a surprise to see them tire at some point in this game.
He added that the team was "really proud with the style we played, with the intelligence that we have performed under pressure".
Win tonight and England will face France in the final after they beat Belgium 1-0 with a Samuel Umtiti header.
After England gave up a tying goal to Brazil in first-half stoppage time in the 2002 Soccer World Cup quarter-finals, Southgate felt coach Sven-Goran Eriksson lacked inspirational oratory in the locker room at half-time.
The penalty shootout win against hosts Russian Federation in the quarter-finals on Sunday seems to have gone a long way towards achieving that. "We are looking to keep breaking those barriers down".
The whole Good Morning Britain team donned their waistcoats to cheer on the England side on Wednesday morning.
All we can say is that for two of these four sides that answer will come sooner rather than later, as today (*producer jump zoom*): one of these nations is going home.
Southgate spent time in the United States at the start of the year, watching the Super Bowl but also National Basketball Association games in a bid to discover how teams got themselves into space near the basket via choreographed moves and plays. We have had the chance to make a difference.
"He knows what he wants and he wears it extremely well but it's always blues and dark colours and he brightens it up with a shirt".
England's dream that "it's coming home" continues, with Dele Alli scoring a second-half victor.
"They should be judged on them as a team".
"I couldn't listen to it for 20 years, frankly", said Southgate.
CROATIA is going nuts about their team's appearance in the World Cup semi-finals - but one group of fans had particular reason to celebrate during their penalty shootout win over Russian Federation. "It has a slightly different feel for me, but it's nice to hear people enjoying it again", Southgate said.