"Our offense did a great job, put us all on their back," Wainwright said.
The 24-year-old Rosenthal is among the major league leaders with 36 saves in 40 chances in his first season as closer. He walked the bases full with a strikeout in the ninth and Seth Maness gave up a two-run single to Abraham Almonte before earning his second save in two chances.
"We needed to get him some help," manager Mike Matheny said. "We didn't feel like we were going to sit around and watch too much without giving him a break."
Three walks was a career worst for Rosenthal, who has walked five his last two appearances along with three hits and three runs in 1 1/3 innings. The hard-throwing righty and his manager believe it's a timing issue and not about fatigue.
"Physically, everything feels pretty good," Rosenthal said. "I think it's just going to be narrowing the sights a little bit, or maybe not trying to do too much."
Rosenthal is among the league leaders with 57 appearances.
"We've worked him pretty hard and we're going to be very careful about how we move forward," Matheny said. "We're not afraid to use the other guys in our bullpen to pick up the games when he can't.
"But as far as his role, he's our closer."
Jon Jay's two-run single highlighted a four-run first inning when the Cardinals batted around against rookie Odrisamer Despaigne (3-4). Peter Bourjos and Tony Cruz each had an RBI single for St. Louis, which took three of four in the series.
Despaigne needed 37 pitches to get out of the first.
"He just couldn't finish off any hitters," manager Bud Black said. "He couldn't get any of his pitches where he needed to get them."
Carpenter's two-run double off Tim Stauffer in the sixth made it a three-run cushion for Wainwright (15-7), who joined the Reds' Johnny Cueto at 15 wins. Milwaukee's Wily Peralta was seeking his 15th later Sunday.
Wainwright allowed three earned runs in seven innings with five strikeouts and one walk, overcoming a handful of rough patches. He hasn't felt locked in for a while.
"It's been a grind for over a month now," Wainwright said. "I'm about ready for it to end."
Wainwright is 5-0 at home with a 1.55 ERA against the Padres, so this was one of his stiffer tests.
"We did a nice job of laying off the breaking balls as the game went on," Black said. "We put together some better swings."
Alexi Amarista and Yangvertis Solarte had an RBI apiece in the San Diego fifth. Jake Goebbert had an RBI triple and scored on second baseman Kolten Wong's wild relay as the Padres pulled within 5-4 in the sixth.
Padres: 3B Solarte has started the last two games after missing a pair with a mild left oblique strain.
Cardinals: OF Matt Holliday got a day off with a minor knee problem, plus has been scuffling at the plate, going 0 for 18 the previous five games.
Cardinals: Justin Masterson (6-7, 5.58) faces the Reds and Mike Leake (9-11, 3.59) on Monday. Masterson is coming off seven scoreless innings against the Marlins, the best of three starts since arriving at the trade deadline.
Jay is 12 for 24 during a nine-game hitting streak and is batting .417 this month. Jay also was hit by a pitch four times in a span of five plate appearances on Friday and Saturday.
"He's doing a nice job of getting on base, whether he's a magnet or not," Matheny said.