The Serbian world number seven lost his serve to 4–5 in the first set, grimaced, and clearly showed that his groin was hurting.
He received a visit from physiotherapists at the bench and after a brief conversation, the star left to receive medical attention in Rod Laver Arena's inner area.
When the 37-year-old returned to the court – with a bandage high up on his left leg – he lost the first set.
Turned to victory
Then came the turnaround.
Djokovic, who has won the Australian Open ten times, took the second and third sets with 6–4 and 6–3 respectively. In the fourth, the star immediately got a grip and eventually secured a semifinal spot after 6–4.
I'm still in the tournament and don't want to reveal too much, he says when asked about the injury during the victory interview.
But the medicine kicked in and it helped. I took another dose – it sounds terrible – but I had to. If I had lost the second set, I probably wouldn't have continued playing.
When the medicine stops working, we'll see how serious it is, but right now I just want to stay in the moment and enjoy the victory.
"When are you going to sleep?"
Djokovic was then surprised to find that his children were still in the stands.
I love you and thanks for the support, but it's one o'clock at night – when are you going to sleep?
Novak Djokovic has now won five out of eight matches against 21-year-old Alcaraz, including one Olympic Games final in Paris last summer.
In the semifinal, he will face German Alexander Zverev, who earlier in the day won 3–1 against American Tommy Paul.
Recovery is all I'm thinking about now, says Djokovic.
