Sinner lost serve midway through the second set but quickly reestablished his advantage and defeated the 23-year-old Shelton in 70 minutes.
“I’m not thinking about the rankings at the moment,” the Australian Open and Wimbledon champion added. “It’s a result of the way I play.
“It means a lot to reach the semi-finals in Paris. It’s been a very long season with some very, very good results that I never take for granted.”
Sinner will face either Alexander Zverev or Daniil Medvedev in the final four games.
Alexander Bublik made his first Masters semi-final appearance with a 6-7 (5-7) 6-4 7-5 win over Australian sixth seed Alex de Minaur, sparking exciting scenes for Kazakhstan’s top player.
The No. 13 seed will next face Canadian player Felix Auger-Aliassime. The ninth seed ended the winning streak of Shanghai Masters champion Valentin Vachero with a score of 6-2 6-2.
