Spain’s Alcaraz dropped just four games in a 6-1 6-2 6-1 dispatching of American lucky loser JJ Wolf in the first round.
The 21-year-old has been struggling with a right forearm injury and wore a compression sleeve during his first-round match, but said afterwards he believed his injury was getting “better and better”.
The Wimbledon champion faces a second-round meeting with qualifier De Jong, who shocked Britain’s Jack Draper in five sets.
The 23-year-old has never reached the third round of a major.
Sinner, who has a burgeoning rivalry with Alcaraz, is looking to better his quarter-final showing in 2020.
He will replace defending champion Novak Djokovic at the top of the world rankings should the Serb fail to reach the semi-finals.