Gareth Southgate had an eye on the future as he road-tested a new defensive formation in Friday's goalless Nations League draw with Croatia.
Southgate moved away from the three-man defence that served him well on England's run to the World Cup semi-finals to try a more flexible system in Rijeka.
The new setup saw John Stones and Harry Maguire line up at the heart of a four-man defence but allowed Eric Dier to join them when England were on the ball, freeing up full-backs Kyle Walker and Ben Chilwell to venture forward.
"We've had success building with the three and with Eric in that position it's perfect for him to drop in, so that at times was the idea," Southgate told Sky Sports.
"There were other times where John and Harry just built the game themselves and Eric was a bit more advanced. It meant we could get our full-backs up a bit higher, so it's good to have that option.
"Without the ball it meant we were able to get higher and get closer to their midfield."
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Expanding on the thinking behind the change, Southgate added: "I don't think you should be rigid and say that's what we're doing and stick with it regardless.
"I've wanted to look at a form after the last few games, where without the ball we've suffered a bit because of the shape, and when I look at some of the young players that are coming through there are wide players and number eights that might suit that system, so I think we have to have an open mind to it, but I thought the players executed it really well.
"What we found in the two matches with Spain and Switzerland in the first half was out of possession we were having to cover too much ground, and both teams pinned our five back with three and we were getting outnumbered in midfield and further forward as well.
"Also, availability of personnel affects that. At the beginning, with the likes of Maguire, when they hadn't played as much international football, to play with the five was helpful to help them bed in.
"Now he's established and John as well they looked more than capable of playing in the four."
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