SAN DIEGO (Interstat) — Ryan O’Hearn’s first-inning grand slam sparked a powerful offensive display and Randy Vásquez delivered seven dominant innings as the San Diego Padres blanked the Milwaukee Brewers 7-0 on Tuesday night at PETCO Park.

In a potential National League playoff preview before a crowd of 44,089, the Padres (87-71) won their fourth straight and clinched the series victory over the NL Central champion Brewers (95-63). The loss ensures Milwaukee cannot reach 100 wins, halting a bid for consecutive 100-win seasons for the first time since 2012-14. The Brewers’ magic number to clinch the best record in the majors and home-field advantage throughout the postseason remains at two over the Philadelphia Phillies.

Vásquez (6-7) was the story on the mound, allowing just one hit while walking one and striking out three over seven scoreless frames. He retired the final 14 batters he faced after giving up a single to Christian Yelich in the third inning. The Padres’ bullpen sealed the combined four-hitter, with Yuki Matsui and Wandy Peralta each tossing a scoreless inning. Peralta struck out two in the ninth.

The game was decided early. San Diego jumped on Brewers starter Bruce Zimmermann (0-1) immediately. Luis Arraez led off the bottom of the first with a single, and after a Xander Bogaerts strikeout, Gavin Sheets walked and Ramón Laureano singled to load the bases. O’Hearn then crushed a 1-1 pitch from Zimmermann over the right-field fence for his 17th home run of the season, a grand slam that gave the Padres a 4-0 lead.

San Diego added to its advantage in the second inning. Mason McCoy reached on a throwing error by Brewers second baseman Brice Turang, and Arraez followed by launching a two-run homer, his eighth of the year, to right field to make it 6-0.

Zimmermann settled in after the rough start, ultimately working six innings and allowing five earned runs on seven hits with one walk and one strikeout. Tobias Myers provided two innings of relief for Milwaukee, giving up one run on one hit—a solo home run to Jose Iglesias in the eighth inning that capped the scoring at 7-0.

The Brewers’ offense never threatened, mustering only four singles. Their best chance came in the eighth inning when Blake Perkins and Joey Ortiz hit back-to-back singles off Peralta, putting runners on first and second with one out. But Peralta induced a fielder’s choice from Yelich and struck out Jackson Chourio to end the threat.

O’Hearn finished 2 for 4 with four RBIs to lead the Padres’ eight-hit attack. Arraez went 2 for 3 with a walk, two RBIs and two runs scored, while Iglesias also had two hits, including his third home run.

The two teams conclude their three-game series, and their regular-season series, on Wednesday. The Padres will look for a sweep while the Brewers aim to rebound before heading home for a final series against the Cincinnati Reds.