SAN DIEGO (Interstat) — Fernando Tatís Jr. returned from a three-game absence and hit a game-altering grand slam in the fourth inning, powering the San Diego Padres to a 7-4 victory over the Arizona Diamondbacks on Friday night at a sold-out PETCO Park.

The win, San Diego’s fifth in its last six games, officially eliminated the Diamondbacks from postseason contention and ensured the Padres will host the Chicago Cubs to open the playoffs. The loss dropped Arizona to an even 80-80 with two games remaining in the season.

A sellout crowd of 44,547 watched as the Diamondbacks struck first. Ketel Marte launched a solo home run, his 27th of the season, off Padres starter Yu Darvish in the top of the first inning. Arizona extended its lead to 2-0 in the third when Jake McCarthy connected for his fourth homer of the year.

The early advantage, however, was short-lived. San Diego’s offense erupted against Arizona ace Zac Gallen in the bottom of the fourth. The inning started with a sharp lineout from Jackson Merrill, but then Xander Bogaerts, Gavin Sheets and Ryan O’Hearn strung together three consecutive singles, with O’Hearn’s driving in Bogaerts to cut the deficit to 2-1.

After Jake Cronenworth struck out, Gallen walked Freddy Fermin to load the bases for Tatís. The star right fielder, who had been sidelined with an illness, worked the count and then unloaded on a Gallen offering, sending a towering grand slam to left-center field for his 24th home run of the season. The blast, Tatís’s fourth career slam, gave the Padres a 5-2 lead and sent the home crowd into a frenzy.

San Diego added another run in the fifth inning in unconventional fashion. Gallen loaded the bases with a walk to Manny Machado, a single by Bogaerts, and a fielder’s choice that included a missed catch error by Diamondbacks shortstop Geraldo Perdomo. After a strikeout of O’Hearn, Gallen walked Cronenworth to force in Machado, extending the Padres’ lead to 6-2 and ending Gallen’s night.

Darvish earned the win, improving to 5-5. He allowed two runs on six hits over five innings, striking out four. The loss was charged to Gallen, who fell to 13-15 after surrendering six runs, five earned, on eight hits and four walks in 4 2/3 innings.

Arizona mounted a threat in the eighth inning against the San Diego bullpen, clawing back two runs without the benefit of a hit. Padres relievers Bradgley Rodriguez and Wandy Peralta combined to issue four walks in the frame, forcing in runs to make the score 6-4. Mason Miller was summoned from the bullpen and struck out Jorge Barrosa with the bases loaded to extinguish the rally.

The Padres responded immediately in the bottom of the eighth, restoring a three-run cushion. Luis Arraez, who extended his hitting streak to 14 games with his 22nd career four-hit performance, singled and scored on a sharp RBI single by Jackson Merrill to make it 7-4.

Miller returned to the mound for the ninth and closed the door, striking out two in a perfect inning to secure his 22nd save of the season. Miller’s final line was 1 1/3 perfect innings with three strikeouts.

Offensively, the Padres out-hit the Diamondbacks 12 to 8. Arraez led the way with his four hits, while Perdomo had two of Arizona’s eight hits, both doubles.

The victory improved the Padres to 88-72 and, coupled with the Cubs’ loss, prevented Chicago from clinching home-field advantage for their upcoming Wild Card Series. The two teams will continue their three-game series Saturday night at PETCO Park.