Alexander Zverev slated ATP chiefs after a punishing defeat to Carlos Alcaraz in the Madrid Open final, but described his Spanish conqueror as "the best player in the world" and predicted he would win a stack of grand slam titles.

German star Zverev was fuming over his court scheduling this week, claiming late-night contests meant he came into the title match in no fit state to compete as he described tournament bosses as "an absolute disgrace".

He claimed he had only been able to get to bed at 5.20am after a late-night semi-final victory over Stefanos Tsitsipas on Saturday.

While Zverev had warm words for 19-year-old sensation Alcaraz, he felt he had cause to feel aggrieved at his handling by tennis organisers after his 6-3 6-1 final reverse. 

"I want to congratulate Carlitos," he said in an on-court interview. "Right now, you are the best player in the world. It is great for tennis that we have such a new superstar that is going to win so many grand slams, that is going to be world number one, and I think is going to win this tournament many more times."

Later, in a news conference, Zverev said Alcaraz had been "playing amazing".

"But one thing I have to say is that the ATP's job was an absolute disgrace this week," Zverev said, according to tennismajors.com. "Two days ago I went to bed at 4:00, 4:30am. Yesterday I went to bed at 5:20am. If any normal person goes to bed one night at 4:00am, the next night at 5:00am, it will be a tough time just to be awake for them.

"And for me to play a final against Carlos Alcaraz, who for me is the best player in the world right now, in a Masters 1000 event, the next day, it is difficult."

There is little doubt Alcaraz, who will now skip the Internazionali d'Italia to rest before the French Open, is only going to keep progressing.

After beating Rafael Nadal and Novak Djokovic this week before overcoming Zverev in the title match, he will leap three places to sixth in the ATP rankings on Monday, having followed up last month's triumph in Miami with his second Masters 1000 title.

"It feels great to be able to beat these players," Alcaraz said. "To beat two of the best players in history and then Zverev, the world number three. 

"I would say this is the best week of my life. I am 19 years old, which I think is the key to be able to play long and tough matches in a row. I am feeling great physically.

"It is a great moment for me. It is the first tournament I watched, so lifting the trophy today is so emotional."