Alexander-Arnold's crossing ability has drawn comparisons with the Manchester United Treble winner.
“There's still a bit to do defensively on positioning and awareness but he's had some fantastic experiences already in a very short career. He's heading in a really good trajectory," said Southgate who was asked whether he was England's best crosser since Backham.
“He's his own player. His technique for his crossing is fantastic. In training yesterday he wandered down the other end of the training pitch with a bag of balls, put one down. They had a wall up, he whipped it round the wall into the top corner then just walked off.
“So we said: 'OK, a bit of pressure training.' He's got great belief in his delivery. When he was taking his corners, actually, there was too much (whip) on them. But it's a great asset to have."