SAN DIEGO (Interstat) — The San Diego Padres stormed into the postseason Sunday, completing a three-game sweep of the Arizona Diamondbacks with a 12-4 victory at a sold-out PETCO Park.

In a game that spanned the afternoon and evening before an announced crowd of 45,072, the Padres offense erupted early and often, providing a dominant final tune-up before they head to Chicago for a National League wild-card series against the Cubs starting Tuesday.

Arizona’s Ketel Marte jolted the Diamondbacks to a quick lead, launching a solo home run, his 28th of the season, off Padres starter JP Sears in the top of the first inning.

The lead was short-lived. San Diego answered with a five-run bottom of the first, chasing Arizona starter Brandon Pfaadt after he recorded just one out. The rally started with a Fernando Tatis Jr. single and a Ryan O’Hearn single. Manny Machado then drove in Tatis with an RBI single. Jackson Merrill followed with a two-run double, and Xander Bogaerts capped the inning with another two-run double to give the Padres a 5-1 lead.

Machado extended the Padres’ advantage in the third inning, leading off the frame with his 27th home run of the year to make it 6-1.

Arizona scratched out a run in the top of the third on a double play groundout by Tim Tawa, but the Padres broke the game open with a three-run fifth inning. Merrill was again in the thick of the action, lashing a two-run double to center field. A fielder’s choice from Gavin Sheets later in the inning brought home another run, pushing the San Diego lead to 9-2.

The Padres added three more runs in the seventh. Jake Cronenworth hit an RBI single, and Jose Iglesias cleared the bases with a two-run double, bringing the score to its final margin of 12-4.

Arizona managed two unearned runs in the ninth inning on a fielding error by first baseman Ryan O’Hearn, but it was not enough to avert the sweep.

Sears earned the win for San Diego, improving to 9-11. He pitched 5 2/3 innings, allowing two earned runs on seven hits while striking out four. Pfaadt took the loss for Arizona, falling to 13-9 after surrendering six earned runs in just one-third of an inning.

Merrill led the Padres’ offensive charge, going 2 for 3 with a walk, three RBIs and two runs scored. Machado finished 2 for 2 with his home run, two RBIs and two runs scored. Reliever Bradgley Rodriguez was sharp out of the bullpen, striking out three in 1 1/3 perfect innings.

For Arizona, Marte’s first-inning homer was a bright spot in an otherwise frustrating game that saw the Diamondbacks strand multiple runners and ground into two double plays.

The victory secured a 90-72 final record for the Padres, who now turn their attention to the Cubs. The teams split their six regular-season meetings. The loss concluded Arizona’s season with an 80-82 record.

The game time was 3 hours, 11 minutes.