In the sixth, everything fell into place.
"We did take really good at-bats," Grandal said. "We had guys who kept battling and walking, so that was a plus. That could have been something that factored into him having that big of a pitch count."
Wacha departed after 112 pitches, the no-no and the lead both long gone. He wasn't blaming fatigue.
"I felt like I was in control for a lot of that inning," Wacha said. "I just got behind Grandal and he put a good swing on a heater, hit it out of here."
Carlos Frias (4-2) allowed an unearned run and five hits in seven innings, an impressive bounce back after surrendering a career-worst 10 runs his last time out. Frias bunted for his first career hit in the seventh.
"Really, the key is Carlos. Carlos keeps us in the game," manager Don Mattingly said. "You get down three or four runs, you start to get desperate."
Frias said he didn't worry too much about his last outing and just put his trust in his catcher, Grandal.
"You put that one away and get ready for the next start," Frias said. ""I threw everything he wanted me to,"
Howie Kendrick's RBI single tied it at 1 two at-bats before Grandal, activated from the 7-day concussion disabled list earlier Saturday, hammered a 3-1 pitch an estimated 435 feet to left-center.
Grandal grounded out and walked his first two at-bats but felt he had been struggling.
"I was just trying to get my timing back, and then it just happened that he made a mistake," Grandal said. "Probably the only mistake he made all night and I was able to capitalize on it."
The Dodgers, held hitless for the first 5 1/3 innings, ended a drought of 42 consecutive scoreless innings on the road, including a 3-0 loss in the series opener Friday.
"It was a relief, for sure," Mattingly said. "It was good to put a few up."
Wacha (7-1) gave up four runs and three hits in 5 2/3 innings for the Cardinals, whose five-game winning streak ended. He had entered tied for the league lead in victories and among the best with a 1.87 ERA.
The game was delayed 2 hours, 20 minutes before the first pitch, and precipitation resumed pretty much non-stop in the bottom of the first to scatter a sellout crowd of 44,754 before Grandal's drive estimated at 435 feet to left center put the Dodgers up 4-1.
Jhonny Peralta had a run-scoring groundout in the first but also grounded into two of the Cardinals' three double plays and struck out.
Wacha was the NL championship series MVP as a rookie in 2013, twice besting the Dodgers and ace Clayton Kershaw. This was his first regular-season game against them.
Dodgers: Mattingly says OF Yasiel Puig (hamstring) may start a rehab assignment soon.
Cardinals: Matt Holliday was back in the lineup a day after being sent home with flu-like symptoms. He extended his franchise-record streak to 44 consecutive games reaching safely to start the season with a walk in the fourth, then was taken out feeling ill.
Carlos Martinez (4-2, 3.54) hasn't allowed a run in 13 1/3 innings, a season-long scoreless streak for St. Louis. Brett Anderson (2-2, 3.47) worked a season-high seven innings his last time out and is 1-1 with a 2.12 ERA in May.
The Cardinals will mark the one-year anniversary of the late Oscar Taveras' major league debut on Sunday, with members of the players' family scheduled to attend. Taveras and his girlfriend were killed in a car crash in the Dominican Republic in the offseason.
Nats win 8-2; Brewers' Peralta exits with shoulder tightness
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