England were heading for defeat before Jude Bellingham's wonder goal send the tie into extra-time. Harry Kane then found a winner.
Southgate told BBC Radio 5 Live: “With 15 minutes to go you wonder if he is out on his feet, but him and Harry Kane produce those moments and that is why you don’t make changes when people are clamouring for more changes.
“I’ve said for a long time he is doing unbelievably well. I think I understand his world better than a lot of people. His world is incredibly different.
"He’s had an incredible impact even though he is only a young man. He will say things and react to things like a young man will, but can create moments that change big games and that’s what he has done here.”
Declan Rice joined the chorus of praise, adding: “It was a big moment for a 21-year-old. It takes a lot of guts to do something like that. People don’t understand what you have to go through to get over the line.”