Alli began the tournament with a sparky first-half performance in the opening fixture against Tunisia but limped off with a thigh injury that kept him on the sidelines for the remainder of the group phase.
The Tottenham playmaker returned to the starting XI to face Colombia only to find himself pushed deeper than he might like in a frenetic encounter and was once again struggling for fitness by the time he made way in the second half.
Now, with the Three Lions chasing a first appearance in the final four since 1990, Southgate believes the 22-year-old is ready to catch fire.
For that to happen, he needs to impose himself as an attacking threat and the manager will give him full licence to do so.
“In terms of Dele, I thought his performance against Tunisia was as good as he’s had since I’ve been England manager. He’s at his best making those forward runs and really threatening the opponents with those runs from midfield,” said Southgate.
“Maybe we need to encourage him a little bit more to get into those areas where I think his strengths lie and where he can have the biggest impact on the game.
“That’s something we’ve got to think about tactically. We do want to create more clear chances and I think we can create more.
“The other night (against Colombia) the game was a little bit different and he did a really diligent job without the ball for us. It’s about creating good chances and being able to break down a defence that will be packed. Dele is a player who gives us a different option to do that.”
Alli’s fitness does not appear to be a concern, with the only lingering doubts concerning striker Jamie Vardy - who would not be in the first XI regardless - and his recovery from a groin complaint.
“We just need to check with Vardy again,” said Southgate. “He completed what we hoped he would (in training), but slightly separate from the team. We’ll check if there is any reaction to that. Everyone else trained.”
England head into the game in Samara seeking their first clean sheet of the competition.
That may raise eyebrows given their stingy record in qualifying, where they conceded only three times in 10 games and shut their opponents down eight times.
Southgate, though, has restructured his side since then - favouring more flair and forward momentum in midfield at the expense of the defensively-minded Eric Dier.
He admits there is still some fine-tuning to do to perfect the system and recognises the need to tighten up at the back if England are to stay involved as the World Cup builds to a crescendo.
“We’ve been disappointed not to keep clean sheets and the value of those in a tournament is clear, especially towards the latter stages,” he said.
“It just shows that we still have room for improvement in our game.”
“We’re controlling games with the ball, but we can create more chances and we can defend better.
“We’re an emerging and evolving side, a long way from perfect. Sweden is another great test for us on a fantastic stage.”
Southgate has been teetering ever closer to ‘national treasure’ status over the past three weeks, as much for the considered, self-deprecating nature of his public appearances as his tactical acumen.
As well as becoming the subject of several social media memes and driving a upturn in waistcoat sales, he has also been conferred the honour of a personalised chant from the England faithful.
The song, to the tune of Atomic Kitten’s ‘Whole Again’ includes the unlikely couplet ‘Southgate you’re the one/You still turn me on’.
“That’s not as questionable as most of the lyrics of the songs that have been sung about me in the past,” he said with a smile.
“I’ve no problem with that. I’ve been in football for 30-odd years. You’re never as good as people say when things are going well, or as poor as people say when things are going badly.
“Do I like the song? They wouldn’t be my first-choice band, but it’s nice to be recognised by the supporters.”