Snell said he was more excited about hitting 99 mph and wanted to talk to reliever Adrian Morejon, a hard-throwing lefty.
“In the sixth inning I was like, ‘Oh wow I’ve got a no-no going' but I was so hyped up about 99,” Snell said. "The ball just felt really good tonight. It was just coming out.
“Morejon always talks about how he has all this velo and I finally hit 99 in front of him so I'm pumped,” the lefty said. “I was really pumped about the 99. Really pumped. Whatever happened, that was the highlight.”
Snell, the 2018 AL Cy Young Award winner while with Tampa Bay, said this performance “was up there” among his best games. "It was good one. But we'll continue to try to top it.”
The Padres have shut out the Cardinals in the first two games of the three-game series, keeping Pujols at 698 career homers.
San Diego stayed 1 1/2 games ahead of Philadelphia for the NL’s second wild-card spot.
The left-handed Snell had shut down Pujols and the Cardinals into the seventh, retiring the slugger twice and issuing just two walks. But with the Padres shifting the right-handed Pujols, the 42-year-old slugger drove a ball through the wide-open right side of the infield for an easy hit on a 3-1 pitch, Snell's 107th of the game.
“He's a good hitter,” Snell said.
“I thought if I got a quick inning there I might have gotten into the eighth," he added. "Who knows. It's just tough; 13 strikeouts, like it's going to be really tough going nine without throwing like 140, 150 (pitches).”
Juan Yepez followed with a single before Snell struck out Paul DeJong for No. 13.
Josh Hader pitched a perfect ninth for his 34th save.
The Padres took a 1-0 lead when Austin Nola singled in Kim Ha-seong with two outs in the second against Miles Mikolas. Josh Bell was thrown out earlier in the inning trying to score on a grounder to shortstop.
Mikolas (11-13) allowed an unearned run on three hits in six innings, struck out six and walked two.
San Diego's Juan Soto walked leading off the eighth, becoming the first player since 1906 to walk 500 times before turning 24.
Cardinals RHP Jack Flaherty (0-1, 5.09 ERA) and Padres RHP Joe Musgrove (10-7, 3.16) are scheduled to start in the series finale Thursday afternoon.
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