Tatis hit the solo shot in the sixth inning of the Padres' 10-3 setback in the series opener Monday at Petco Park in San Diego. The Diamondbacks led 9-0 entering the bottom half of the frame.
Eric Hosmer hit a leadoff double to spark the rally for San Diego before Manny Machado knocked Hosmer to third base with a single. Franmil Reyes plated Hosmer on a sacrifice fly, before Wil Myers flew out to right field.
Tatis then stepped in to face Diamondbacks reliever Merrill Kelly. The righty threw the rookie a 90-mph fastball and Tatis tattooed the offering for a line drive to left field. The two-run shot easily cleared the outfield fence and ended up deep in the left field seats.
Tatis' bomb traveled a projected 395 feet and had an exit velocity of 107 mph, according to Statcast. The Padres' top prospect was 1-for-4 with two RBIs, a strikeout and a run scored in the loss. He is hitting .222 on the season.
"Got that one out of the way," Tatis told reporters, according to MLB.com. "First one, here we go. A lot more to come."
The 20-year-old got the ball back from a fan after the game and exchanged it with a different ball, which he autographed. Tatis said he plans to give the ball to his dad, who played 11 Major League Baseball seasons for the Texas Rangers, St. Louis Cardinals, Montreal Expos, Baltimore Orioles and New York Mets from 1997 to 2010.
Tatis and the Padres host the Diamondbacks again at 10:10 p.m. Tuesday in San Diego.