Carlos Alcaraz admitted that he made a “big mistake” in his Australian Open quarter-final defeat to Novak Djokovic when he saw his opponent was struggling with injury during the second set.

Djokovic managed to battle from a set down to reach a 12th Australian Open in a vintage display from the 37-year-old, but Alcaraz said he let the Serbian back into the match by taking his foot off the gas in the second set.

Djokovic took a medical timeout late in the first set, leaving the court before returning with strapping around his left leg, and Alcaraz said he thought the match against the 24-time grand slam champion would be “easier” from there.

Djokovic admitted he would have retired from the match had he gone two sets down to Alcaraz, but he started to play more aggressively in the rallies and survived to level the match before the painkillers kicked in at the start of the third set.

Alcaraz, who now trails his head-to-head against Djokovic 5-3 after suffering a second consecutive exit at the Australian Open quarter-finals, congratulated his opponent but regretted that he did not put the match away.

“Honestly, I felt like I was controlling the match, and I let him get into the match again. I’m going to say that was the biggest mistake that I made today,” Alcaraz said in his post-match press conference.

“In the second set I had to play a little bit better just to push him even more to the limit. He had issues just moving a little bit in the second set. I had to push him a little bit more just to the limit, and I didn’t.

“After that, I think he started to feel better and he started playing at such a great level. That was my biggest mistake today. Obviously when Novak is at this level, it’s really difficult. I think I had my chances. It was a really close match.

“I think most of the crucial points went to his side. When Novak is playing at this level, it’s really difficult to find the way.”

Alcaraz continued: “When you are seeing someone that is struggling physically a little bit, it’s kind of you not playing the same level. It seems like, okay, it’s going to be easier.

“At the same time in your mind you’re thinking, like, Okay, I have not to make mistakes. Probably you’re not hitting the ball the same way that you’re hitting before. I think that’s it.

“I think he did great, great hits, great shots. He started to play more aggressively, try not to move so much in the second set. He made a few of them, which made him stay up in the set, go break up. After that, as I said, it was really difficult to overcome that.”

Djokovic described his victory over Alcaraz as one of finest at the Australian Open, and an epic quarter-final adds another chapter to their generational rivalry after last summer’s Olympics final and two Wimbledon showpieces.

“Every time that we play against each other, I think it’s a guarantee,” Alcaraz said. “We push us to the limit, each other. I think we’ve played great points, great rallies. It was really tight in the third, the fourth set. The whole match, I guess.

“I’m just lucky to live this experience. I’m 21 years old. From these matches, I’m getting so much experience about how to deal with everything. I’m not going to hide.

“I’ve done great things in tennis already, but playing against one of the best in history of our sport, these kind of matches help me a lot in the future to be better.

“I’m just happy to be able to live this experience. It’s great hearing those words from someone who played historic matches and achieved historic things.

“I’m leaving Australia with my head up. I’m really happy about hearing those words from Novak.”