MELBOURNE: Serena Williams and Naomi Osaka face their toughest tests so far when the Australian Open enters the last 16 stage on Sunday, while Novak Djokovic faces a battle to recover from a potentially tournament-ending injury.
Djokovic has been given the maximum amount of time to recover from a midriff muscle tear that left him grimacing on virtually every shot during his attritional, five-set win over American Taylor Fritz late on Friday.
The Serb world number one, looking for a record-extending ninth Australian Open crown, will feature in the late-night match on Rod Laver Arena against big-serving Canadian Milos Raonic.
Djokovic, who chose not to practise on Saturday to seek…
