There was no drama on the women's side as holder Iga Swiatek continued her quest for a fourth Roland Garros trophy by hitting top gear during a 6-0 6-2 victory over 2019 runner-up Marketa Vondrousova to also reach the semi-finals.
American third seed Coco Gauff earlier fought back to beat fan-favourite Ons Jabeur 4-6 6-2 6-3 and will take on Swiatek in a tantalising rematch of their 2022 final, which the Pole won.
Roland Garros was rocked towards the end of Sinner's routine win as organisers announced that Djokovic had withdrawn from his 2023 final rematch with seventh seed Casper Ruud in the last-eight on Wednesday.
It meant that Sinner, who ended Djokovic's quest for an 11th Australian Open title en route to his first Grand Slam trophy in January, will also take his top ranking next Monday and become the first Italian to do so.
Djokovic needed a superhuman effort and five sets to subdue Argentine Francisco Cerundolo on Monday after being dragged the distance for a second straight contest and the Serb aggravated the injury he had been carrying by slipping on court.
The French Open said MRI results revealed that Djokovic, who played on with pain-killers, had suffered a torn medial meniscus that prompted him to take the decision.
It was the latest in a series of unfortunate events for the 37-year-old, who won three out of the four majors last year but has looked off the pace this season, with defeats and an injury threatening his bid for Wimbledon and Paris Olympics glory.
Even as Djokovic arrived at Roland Garros to clean out his locker, Sinner was easing to a 6-2 6-4 7-6(3) win over Dimitrov and the 22-year-old said he had achieved a lifelong dream, even if it was not the way he expected to.
"What can I say? First of all it's every player's dream to be number one. On the other hand, seeing Novak retiring here is, for everyone, disappointing. I wish him a quick recovery," Sinner said.
The Australian Open champion will renew his great rivalry with Carlos Alcaraz in the semi-final, after the two-times Grand Slam champion put on a clinical performance to beat former Roland Garros runner-up Stefanos Tsitsipas 6-3 7-6(3) 6-4.
Alcaraz dropped only three of his first-serve points in the first set and held his nerve through the tiebreak to halt the Greek's mid-match comeback, before delivering one of his superb dropshots on match point.
The Spaniard assured the crowd at Roland Garros that his meeting with Sinner would not disappoint, with the Italian playing at the top of his game.
"It's going to be a really difficult challenge for me. I'm ready to take that challenge," said Alcaraz. "It is the match that everybody wants to watch and I'm sure that he's going to show his best tennis, myself as well."
The pair are evenly split with their career head-to-head record at 4-4. Alcaraz won their most recent meeting, a semi-final match at Indian Wells this year.
"You have to run like it is a marathon, you know, side-to-side... Everything he does, he does it perfectly," Alcaraz told reporters. "I think it is the hardest thing to face Jannik. At the same time I love that. I love these kind of matches."
