Ageless Novak Djokovic won an epic generational clash against Carlos Alcaraz on Tuesday to stay on track for an 11th Australian Open title with Alexander Zverev next in the semi-finals. The 37-year-old Serb, who is chasing a record 25th Grand Slam crown, outlasted the Spaniard, 16 years his junior, 4-6, 6-4, 6-3, 6-4 despite having his left thigh heavily strapped.