Updated

Shelby Miller struck out seven over seven stellar frames and the St. Louis Cardinals used a third-inning outburst to down the San Francisco Giants, 8-0, in the opener of a day/night doubleheader Saturday at Busch Stadium.

Miller (6-3) scattered six hits and a walk to notch the victory, while St. Louis' offense erupted for seven runs and nine hits in the third to provide the rookie right-hander with more than enough run support.

Daniel Descalso had a pair of hits, an RBI and a run scored in the rally, while Tony Cruz contributed a two-run double for the Cardinals, who have won eight of their last 10 games.

Matt Cain (4-3) pitched perfectly outside of the third inning, but was charged for seven runs on nine hits while striking out nine over six innings.

"I made a good bit of mistakes, a lot of pitches over the plate," Cain admitted. "I just made a lot of bad pitches."

Brandon Crawford finished with three of the seven hits for the Giants, who have lost four of their last five.

Cain retired the Cards in order over the first two frames before running into trouble in the third.

Descalso got things going with a leadoff double and Pete Kozma followed with a single before Miller's sacrifice bunt found runners on second and third.

Matt Carpenter and Jon Jay then ripped consecutive RBI singles to give St. Louis a 2-0 lead.

After Matt Holliday was called out on strikes, Allen Craig and Matt Adams stroked back-to-back run-scoring singles to push the lead to 4-0.

Cruz followed with a two-run double to center before Descalso capped the outburst with a base hit to left to score Cruz for a 7-0 advantage.

"We know that you've got to put an inning together when you can," St. Louis manager Mike Matheny said of facing Cain. "Fortunately, we had one inning where we can."

St. Louis tacked on a run in the eighth after Adams worked a one-out walk and Cruz followed with a double for the Cardinals' lone hit outside of the third inning. Descalso plated Adams with a sac fly to account for the final margin.

Game Notes

Friday's series opener was postponed due to rain, causing Saturday's doubleheader ... In the nightcap, Madison Bumgarner takes the mound for the Giants against St. Louis right-hander Adam Wainwright ... The Giants fell to 9-16 on the road ... St. Louis went 7-for-10 with runners in scoring position while the Giants finished 0-for-9 with RISP ... St. Louis pitcher Keith Butler made his major league debut and pitched a scoreless ninth inning.