After his goalscoring World Cup debut against Iran two weeks ago, Bellingham drove England into the quarter-finals with a commanding display in Sunday’s 3-0 win over Senegal.
He set up the opener for fellow midfielder Jordan Henderson and then produced an electrifying run from deep inside his own half to launch the attack that led to Harry Kane making it 2-0 moments before the interval.
His assist for Henderson made him the first teenager to assist for a World Cup knockout-round goal since 1966 when records began to be kept.
“I don’t think we could have predicted how quickly Bellingham could mature. In the last five months that has gone to another level,” Southgate said after the game.
England teammate Phil Foden, 22, who set up two goals on Sunday, predicted Bellingham would become the best midfielder in the world.
“I don’t want to big him up too much because he is still young, but he’s one of the most gifted players I have ever seen,” Foden said. “He has no weakness in his game.”
Henderson, whose performance was also key to England’s victory, added: “I can’t keep saying nice things about him because we’re talking about a one-off.”
England were struggling to contain Senegal in the first half but Bellingham suddenly seized control of the match, and his first-half statistics said it all.
He won the most duels (eight), tackles (three), won possession twice in the final third and completed 23 of 24 passes, the best ratio of any player on the pitch.
Former England defender Rio Ferdinand was one of several pundits to marvel at his performance.
“Jude Bellingham is 19, I want to see his birth certificate,” he said on Twitter.
England will take on France in the quarter-finals on Saturday with a victory seeing them match their 2018 run to the semi-finals, but with Bellingham in such form they will be confident of going two steps further.