Manchester United captain Harry Maguire will return to the England squad for Friday's Euro 2020 clash with neighbours Scotland.
Maguire has not featured since suffering ankle ligament damage nearly six weeks ago.
But his inclusion in Southgate's squad despite fitness concerns spoke volumes of his importance to the Three Lions' chances of winning the European Championship for the first time.
"Harry will be involved tomorrow," Southgate said at his pre-match press conference on Thursday. "The decision we've got to make is whether he's ready to start but we're really pleased with his progress.
"He's trained with the team for four or five days now and had no reaction. Each session that he's involved with he gets more confident and I think he's on a really good path."
After a 1-0 win over Croatia to start their tournament, England can seal their place in the last 16 with another three points at Wembley.
Harry Kane failed to fire in that opening game, but he admitted his perspective has been impacted by the cardiac arrest suffered by his former Tottenham teammate Christian Eriksen in Denmark's 1-0 defeat to Finland on Saturday.
Eriksen, 29, is to have a heart defibrillator implanted after he suddenly collapsed on the field.
Kane and Eriksen spent seven-and-a-half years together at Spurs.
"It's been difficult. Obviously to watch it last week and see it happen was really hard. Thankfully Christian is alive and seems to be doing well," said Kane.
"I've not had no contact with him personally but my wife has spoken to his wife and from what I understand everything's going in a good way.
"Obviously we've had to try and switch off from it and focus on the game but of course Christian is in all of our hearts. Not just our team but the whole football family.
"It's a reminder of how quickly things can change in life. Never to take things for granted."