Novak Djokovic faces the sternest test of his Australian Open title defence when he meets Italy's Jannik Sinner in the semi-finals on Friday.
The world number one, chasing a record 25th Grand Slam title and 11th triumph in Melbourne, has not lost a match at the tournament in more than six years.
But Sinner has won two of the pair's past three meetings, beating the Serb twice in 12 days in November.
In the other semi-final, Daniil Medvedev takes on Alexander Zverev.
Live text commentary on both matches is available on the BBC Sport website and app from 03:30 GMT, with radio coverage on BBC Radio 5 Sports Extra from 08:00.