"Let me tell you, whether we win or lose the game, my life will not change", he said. "What is that all about?"
Strong, mobile, indefatigable and good in the air, Mandzukic looks to make life as hard as possible for the defence, stretching play to allow the likes of Modric the space they need to get into the danger zone around the box. "Just some mobility exercises".
It's not just the fans back home who are enjoying England's historic run to the last four; the players and staff are equally exuberant. But underneath it all, there remains the serious business of attempting to become world champions for a second time.
Here, Sportsmail's expert columnists give their views on whether England can beat the Croatians and make it all the way to the final.
However, Southgate refuses to accept the idea that England will be significantly fresher.
"Our country has had a long time of suffering in terms of football", he said.
"We know the quality of their players and the spirit they have as a nation".
"'Our country has been through some hard moments in terms of its unity", he admitted.
Before their arrival in Russia, England had not won a knockout game since the 2006 World Cup.
Wednesday's game will see Lovren reacquainted with Kane, who has carried his prolific form in the Premier League to Russian Federation and is the leading scorer at the tournament with six goals. For sure you are coming home, but I hope not with the trophy. "I couldn't listen to it for 20 years, frankly".
I expect Harry Kane and Harry Maguire to have an influence again but the key man for me will be Dele Alli.
"We don't really care about who we play or who are the favourites". "We've got to be prepared for them with the likes of Luka Modric in the team, who's a fantastic player".
"We have emerging leaders". There was a lot of leadership in the group.
Southgate explained: "We are enjoying the journey". That is what these guys have done.
"We are concentrating on what's going on now".
"We have made several pieces of history in the tournament and we're just looking to keep breaking those barriers down".
Croatia are a challenge for England.
Croatia have needed penalty shoot-outs to overcome Denmark and Russian Federation in the knockout stage.
Meanwhile, social media has been awash with support for the England team with several videos of celebrations following the win over Sweden going viral.
"I've played against Modric a few times: he's a world-class player, one of the best I've played against".
"Others, too, because they have threats from different areas".
England manager Gareth Southgate and Harry Kane celebrate their entry into FIFA World Cup 2018 semifinals.
"I was not a renowned fashion icon through my playing career so it's rather odd to be one now", Southgate joked. Kevin De Bruyne is, in fact, the only player to have created more chances left at the tournament than Modric.