After the ineffective deployment of his favoured 3-4-3 formation in Denmark, England boss Gareth Southgate is presented with another opportunity to experiment with formations as preparations for next summer's European Championships resume.
Settling on a defensive system that utilises the wealth of talent at Southgate's disposal, while providing the platform for England's attack to thrive, is now as crucial an objective as any after September's stalemate in Copenhagen.
Having shied away from the three-man defence that underpinned England's success at the 2018 World Cup, Southgate reverted back to it for the trip to Denmark but his experimental side struggled to get to grips with the system, leaving him very much back at the drawing board.
So should Southgate persist with 3-4-3 or settle on four at the back? Ahead of Thursday's friendly against Wales and Sunday's Nations League clash with Belgium, Sky Sports pundits Gary Neville and Jamie Carragher assess the options...
THE CASE FOR 3-4-3...
'Adaptation over time'
Sky Sports' Gary Neville:
"I like the 3-4-3 system for this group of players. I am not sure there is a back four that he could pick that would give me real confidence that he could go on and do well in a tournament.
"I thought at the World Cup in 2018, the 3-5-2 worked well for England. I do think the formation had its faults, with the three in midfield not being able to cover the width of the pitch.
"But that is where the 3-4-3 in attack can help because it becomes a 5-4-1 in defence. Gareth knows that. He talked about accelerating the game when Mason Mount came on [against Denmark] and he changed the game because he got into pockets and we started to see Harry Kane come alive more.
"Mount connected defence to attack from back to front and the other midfield players had better options. It all looked better straight away. So it is all about the adaptation of that model over this period of time.
"Against Denmark, it was never going to work. Eric Dier, Kieran Trippier, Raheem Sterling, the two in midfield, the balance of that team was never going to deliver good football."
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Issues at No 10?
Sky Sports' Jamie Carragher:
"The 3-4-3 system is one that is creeping into the Premier League. We have seen Arsenal do it, Wolves play it a lot. It feels like there are a few teams doing this where you keep your two wide players and your centre-forward up.
"But it feels like whatever system that you play now there is no number 10. You automatically think of Jack Grealish, Mount, Ross Barkley and James Maddison in that number 10 role but where do they fit in with both systems that Gareth looks to be going to play?
"Even in the Premier League now there is a dearth. The role has almost become defunct and you wonder where those players will fit in.
"I know they can still play in little pockets, but I just wonder how Gareth is ever going to work these players in. The only way is if he plays with two number eights, perhaps."
Left-footed centre-back dilemma
Could the selection of a left-footed centre-back address England's imbalance and bring attacking players who were on the fringes in Denmark into play?
Sky Sports' Gary Neville:
"I do agree that it is absolutely preferable. Ben Chilwell could play there with Harry Maguire and Joe Gomez, with potentially Shaw outside him at wing-back, particularly with a holding-midfield player.
"I just don't think that a left-sided centre-back with a left foot would have unlocked the performance [against Denmark]. It was more than that. They were immobile up front. The two in midfield, no rotation. Trippier was always cutting back."
Sky Sports' Jamie Carragher:
"After the draw in Denmark, Gareth was asked about that left side of the defence and he went straight to Trippier, but I would look to Dier as a left-sided centre-back.
"It is no criticism of him, it is just that anyone in that position who is right footed goes back to the middle centre-back or the goalkeeper.
"Surely if there is a centre-back who is more balanced on that left side, who can step in that 10 yards then you are looking at your front three and there is movement. A front three is not going to be running all over the place if a back three are passing the ball between themselves."
Sky Sports' Gary Neville:
"OK, let's say that John Stones, Maguire and Gomez are fit. Is Southgate going to play Tyrone Mings? No, he's not. So, with the best centre-backs available, you are always going to have a right-footed centre-back in that position.
"So, while I agree it is preferable, I don't think it can be the end for that system. If you had a brilliant left-footed centre-back in that position, it would be better. But I still think England will end up with a right footer in there."
THE CASE FOR 4-3-3...
'Premier League pedigree'
Sky Sports' Jamie Carragher:
"Gareth wants to look at different systems going into the tournament. He mentions that they have had great success with 4-3-3 against the lesser nations and when they come up against the top teams [he wants to see] how another system might work.
"I think for any manager it is nice to do something different, maybe surprise an opponent at different times, but the system that most top teams play is 4-3-3.
"I certainly think Maguire and Gomez are the best two centre-backs. Let's not forget, we are talking about a centre-back who is the most expensive in the world. We are talking about a centre-back who is part of a Liverpool team who have lost a couple of games and we rate as one of the best teams in the world.
"We should be expecting a lot from them. One is the captain of Manchester United, the other is playing Liverpool. Two of the top teams in Europe."
Problems with centre-back pairing?
Sky Sports' Gary Neville:
"I just don't think that there is a centre-back partnership that is good enough to take Gareth where he wants to be, which is the final of a tournament and winning a tournament at this moment in time.
"Whether it is Maguire and Gomez or Maguire and Stones, I don't think it would be good enough. I think it needs the stability of the three.
"I think Kyle Walker comes into that, by the way, as one of the three, potentially, because I think Trent Alexander-Arnold is the wing-back. I think Walker can play there with his speed. I think Chilwell can play on the left of a back three or potentially Stones.
"I do think with the players that he has got England are better with a three and that is why he has gone back to it. I was surprised that he came off it after the World Cup. It was the one thing that [surprised me]."
'Southgate needs two systems'
Sky Sports' Gary Neville:
"I think there is more to come from 3-4-3 but he will also go back to 4-3-3 too. He needs two systems. He needs a plan B.
"An interesting debate is around Dele Alli, Barkley, Grealish, Maddison. There has always been a cry for these players. On social media, it's: 'Why isn't Jack Grealish on the pitch?'
"I love Jack Grealish. I love James Maddison. I love Dele Alli. I love Ross Barkley. But they will always be challenged from a managerial perspective at international [level] in terms of where you are going to play them.
"Are they good enough to build a team around them? No. Are they better than the players already in the squad? They have to score goals, provide assists, deliver.
"One or two of them need to step up but Alli and Barkley have been around for four or five years now. Maddison and Grealish less so. But there has always been this element with these players. You have got to deliver, score goals and change the game.