The full-time whistle blows. William Saliba clenches his fist and turns to embrace two of his team-mates. Both men are more than a decade older but it is Saliba’s arms that envelop them, his battle cry that roars in their ears. This, it is clear, is not an ordinary 18-year-old.



Saint-Etienne have beaten Monaco by a goal to nil. Their opponent’s star striker, Wissam Ben Yedder, came into the game on a run of nine goals in eight games. And then he ran into Saliba, who calmly secured a third clean sheet in four Ligue 1 appearances.



Throughout the match, there’s a serenity to the way Saliba casually mops up danger. Bernard Diomede, the former Liverpool winger who coached Saliba for France under-20s, has remarked on the centre-half’s “cold blood”. On the field he is impassive, impassable.



And yet, in the dressing room after the game, it is Saliba who leads the celebrations. It’s he who beats out the rhythm of their victory...