Novak Djokovic produced yet another scarcely-believable comeback to stun Carlos Alcaraz in a thriller and reach the Australian Open semi-finals.

The 37-year-old Serb defied injury, age and ranking to win 4-6 6-4 6-3 6-4 against his 21-year-old opponent in Melbourne.

Djokovic, going for a record-extending 11th men's singles title, limped around Rod Laver Arena at the end of the first set after suffering what appeared to be a groin problem.

But, after going off court for treatment, he recovered impressively to continue his bid for a 25th Grand Slam triumph - which would be an all-time record.

Djokovic played aggressively until the pain wore off, allowing him to move more freely and take control of the match.

Spanish third seed Alcaraz became increasingly animated as he struggled to figure out how to turn an engrossing contest back in his favour.

When seventh seed Djokovic sealed victory - at 00:57 local time after a battle lasting three hours and 38 minutes - he roared towards coach Andy Murray.

Djokovic and Alcaraz shared a warm embrace at the net after a highly-anticipated match which lived up to the expectation.

The defeat ends Alcaraz's hopes - for now, at least - of becoming the youngest man to complete the career Grand Slam.

Instead it is Djokovic who advances to the semi-finals, where he will face German second seed Alexander Zverev on Friday.