When Stefanos Tsitsipas made that prediction in 2021, he believed Djokovic was the last giant standing and that his generation was next. Then a 19-year-old Carlos Alcaraz blew that idea apart.

Standing on stage next to Jannik Sinner during the Australian Open’s trophy ceremony, Alexander Zverev believed that a first grand slam title was a world away. “Today he completely outplayed me,” ...