Sources told MLB.com Tatis won the franchise's starting shortstop gig in spring training. The 20-year-old is the son of longtime infielder Fernando Tatis, who played 11 seasons for five teams.
Tatis is the No. 2 prospect in baseball, according to MLB Pipeline. He hit .241 this spring and is a career .280 hitter at the minor league level.
The promotion means Tatis will be eligible to become a free agent a year earlier than he would have been if the Padres called him up April 12.
Tatis will be the youngest player in Padres history to play on opening day. The infielder was first signed by the Chicago White Sox in 2015, but joined the Padres -- along with right-handed pitcher Erik Johnson -- in a 2016 trade for pitcher James Shields.
Louis Urias is now expected to begin the season with the Triple-A El Paso Chihuahuas.
Tatis is an above-average defender and a shortstop capable of hitting for a high average with at least plus power, according to his MLB Pipeline scouting report.
"While he could still outgrow the position, given his remaining physical projection, Tatis' bat could make him a perennial All-Star, perhaps even an MVP candidate, in his prime," the scouting report says.
Toronto Blue Jays third baseman Vladimir Guerrero Jr. is the only prospect ranked ahead of Tatis. Like Tatis, Guerrero is also the son of a former MLB star, but he is not expected to be on the Blue Jays' opening day roster.
The Padres have the top collection of prospects in Major League Baseball, with 10 in the top 100.