Jannik Sinner took an unexpected path to the world number one ranking on Tuesday after Novak Djokovic's French Open withdrawal but the youngster said it was the culmination of years of hard work and represented a proud moment for Italy.

Sinner arrived at Roland Garros needing to reach the final to assure himself of the top spot next week but got confirmation when organisers announced that Djokovic had pulled out with a knee injury sustained in his fourth-round win on Monday.

It meant the 22-year-old, who was informed of the news shortly after his 6-2, 6-4, 7-6(3) quarter-final win over Grigor Dimitrov, becomes the first Italian man to achieve the feat.

"It means a lot to me for sure. It's not the way we all were expecting. He (Djokovic) had two long, tough matches, five sets, so it's tough. The first one he finished really late also," Sinner told reporters.

"It's tough also for the tournament. Novak retiring, it's always tough. Talking about myself, I'm very happy about this achievement. It's a lot of work we put in daily. It's a daily routine. Obviously happy to have this number.

"In two days there's a very important match for me, the semi-finals (against Casper Ruud), so I'm focused about that at the moment. But yes, happy to have this number now."

Sinner, who guided Italy to the Davis Cup title last year, said the country deserved its recent successes.

"It means a lot, but I think it's great for Italy. We're a great country with great coaches and players and we can see this now how this moment is," Sinner said.

"I'm happy to be part of this Italian movement. People, they start to play tennis now more and more, which is great to see. I think that's the most important."

Sinner's game has moved to another level since he started to work with Darren Cahill, who with Simone Vagnozzi helped him win his maiden Grand Slam title at the Australian Open.

"We started to work now nearly two years (ago). It's a huge pleasure for me to have him. I still remember the first week we had in Eastbourne on grass. Immediately I had good feelings with him because he has a lot of experience obviously," Sinner said.

"I know he brought different kind of players to world number one. He had great achievements also with different players. He knows how to adapt to each player and I think this is a quality that's amazing.

"Him and also the combination with Simone is really good. They're two different coaches, but they work together well. They are humble and they respect each other. The combination is very good. I'm lucky to have both of them and the rest of the team."