Novak Djokovic continued his bid for a record-extending 11th Australian Open title with a confident win over American 12th seed Taylor Fritz.
The Serb, seeking a 25th Grand Slam to move past Margaret Court's record of 24, won 7-6 (7-3) 4-6 6-2 6-3 in hot conditions to reach the semi-finals.
He will play Italian fourth seed Jannik Sinner or Russian fifth seed Andrey Rublev in Melbourne on Friday.
"I suffered a lot in the first couple of sets," top seed Djokovic, 36, said.
"I said [to my team] that this match was not an enjoyable match for me at all.
"It was really difficult to find the right timing. It was really hot while the sun was still out.
"We all know Taylor has got one of the best serves in the world. I knew the kind of a threat he poses when he serves on such a high quality."
Djokovic has won his past 33 singles matches at Melbourne Park and is a clear favourite to defend his title.
Sinner and Rublev's quarter-final is not likely to finish until the early hours of Wednesday morning local time after the night session was pushed back to 21:00.
The singles matches on Rod Laver Arena did not start until 13:00. Coco Gauff's win against Marta Kostyuk in the women's quarter-finals took more than three hours before Djokovic needed almost four to beat Fritz.
Djokovic keeps focus to come through
Djokovic calls the Australian Open his "second home", such has been his dominance over the years, and this was another masterful display as he saw off the latest younger challenger.
His most recent defeat in Melbourne remains a fourth-round loss against South Korea's Chung Hyeon in 2018.
With the match starting about 17:00 local time in temperatures of 31C, Djokovic coolly created eight break points in the opening set but became increasingly flustered as he was unable to take any of them.
Djokovic - looking overheated, regularly using ice towels and shouting towards his team - was almost punished when 26-year-old Fritz created two set points at 6-5 with a stunning forehand winner down the line.
However, Djokovic regained his composure to save them and lay the platform to pounce in the tie-break.
Helped by Fritz missing a simple volley for 1-0, Djokovic quickly asserted his authority and wrapped up the opening set after one hour 24 minutes.
Fritz, who had lost all eight of his previous meetings with Djokovic, responded valiantly.
A break of serve in the first game of the second set, before fighting off seven break points, enabled Fritz to level the match.
But he started to be hampered by a foot issue and Djokovic, looking strong as the conditions cooled, broke twice to win the third set.
Now completely in control, Djokovic was under little pressure on his serve and, when he broke for 4-2 in the fourth, the match looked to be heading towards a conclusion.
Fritz rallied once more by immediately breaking serve, but Djokovic broke again before serving out strongly.
BBC