Novak Djokovic labelled Carlos Alcaraz as "special" and praised the Spaniard for "breathing new life into the world of tennis".

Serbian Djokovic defeated Pole Hubert Hurkacz 6-3 6-4 to reach his seventh Madrid Open semi-final, where he will meet Alcaraz, who overcame Rafael Nadal 6-2 1-6 6-3 on Friday.

Victory made 19-year-old Alcaraz the first teenager to beat record 21-time grand slam winner Nadal on clay on the ATP Tour.

Alcaraz has won his last five matches against top-10 opponents and next faces world number one Djokovic for a place in the final in the Spanish capital.

Djokovic was quick to hail Alcaraz, who will play in his third ATP Masters 1000 semi-final on Saturday.

"There are many things that are special about him," Djokovic said in a news conference.

"In the last decades, we have had some incredible champions [as teenagers] like Michael Chang. But, nowadays, we're not used to seeing someone who is a teenager and already breaks into the top 10 and plays at such a high level.

"His growth, his improvement and his trajectory, especially in the last six months, have been incredible.

"He is a very nice guy off the court. I had the opportunity to train with him and spend a little time off the court with him here in Madrid, and I must say that on all fronts, he is great on and off the court."

Quoted by Spanish media, Djokovic said of Alcaraz: "I love watching him play, like many other players on tour. I praise his game without a doubt. It's fantastic for our sport, without a doubt.

"I think it's fantastic that we have a young player who is doing so well and who is breathing new life into the world of tennis."

Alcaraz expressed personal delight after defeating clay-court great and compatriot Nadal, battling back from an injury worry in the second set.

"It means a lot to me. All the hard work I put in every day has paid off," he said in the aftermath of his victory. "To beat Rafa, the best player in history on clay, it means a lot.

"The fall in the second set affected me a lot. When I lost the set I went to the bathroom and thought I would be able to come back to do my best and try everything.

"I wanted to fight until the last ball and that was the key."