Australian Open: Injured Djokovic retires from semi-final against Zverev after losing first set

• Men's singles semi-finals on day 13 of Australian Open

• Novak Djokovic retires injured from semi-final after losing first set to Alexander Zverev

• Djokovic had been bidding for a 25th Grand Slam title - would be an all-time record

• Germany's Zverev into first Melbourne final as he seeks maiden Grand Slam

• Zverev will face either Jannik Sinner or Ben Shelton in Sunday's showpiece

• Use audio icon for BBC Radio 5 Sports Extra commentary (UK only)

Australian Open: Injured Djokovic retires from semi-final against Zverev after losing first set