Jon Jay, Carlos Beltran and Matt Adams homered in a span of seven at-bats off Homer Bailey as the Cardinals took two of three from the NL Central champions.
Matt Carpenter added a two-run homer on a four-hit day. Adams homered for the second straight game and added an RBI double and a walk.
The Cardinals have dominated the Reds at home the last decade, losing just three of 28 series with two splits.
Westbrook (1-1) threw his fourth career shutout, walking four and striking out three. It was his first shutout since Aug. 9, 2006, against the Angels with Cleveland, and his 15th career complete game. He even contributed an RBI single for St. Louis' final run.
Bailey (1-1) had gone 23 straight shutout innings — including his no-hitter against Pittsburgh last season — before the Cardinals broke open a scoreless game with four runs with two outs in the fifth.
BRAVES 8, MARLINS 0
MIAMI (AP) — Evan Gattis hit a three-run homer and Atlanta completed its second consecutive three-game sweep when it beat the reeling Miami Marlins.
Mike Minor (2-0) pitched 5 2-3 innings for the Braves, whose 8-1 record leads the majors. They're off to their best start since 1994, when they began the season 13-1.
The Marlins have the worst record in the big leagues at 1-8. They've scored just 16 runs, and with five consecutive losses they're off to their worst start since the 1998 team began the season 1-11.
Miami kept the game scoreless until the fifth, when Gattis hit his third homer in a six-run inning. The rookie also singled and is batting .391 with a slugging percentage of .826.
Juan Francisco hit a two-run homer off the facade of the upper deck in centre field, Andrelton Simmons drove in two runs and Jordan Schafer had four of Atlanta's 13 hits.
For the second night in a row, the Marlins drew the smallest crowd since their park opened a year ago. Announced attendance was 13,810.
Miami went 0 for 9 with runners in scoring position and is batting .153 in those situations. Alex Sanabia (1-1) gave up six runs, all in his fifth and final inning.
GIANTS 10, ROCKIES 0
SAN FRANCISCO (AP) — Buster Posey drove in three runs while NBA star Kevin Durant cheered him from the stands, Barry Zito pitched another gem and San Francisco completed a three-game sweep of Colorado.
Staked to a quick lead, Zito (2-0) won his 11th straight decision, dating to last year's post-season. San Francisco earned its 16th consecutive victory in games he has started, the longest such run by a Giants pitcher since 16 in a row by Carl Hubbell for New York in 1936, STATS said.
Zito has thrown 14 scoreless innings so far, the deepest the lefty has gone without giving up a run to start a season in his 14-year career.
Posey hit an RBI triple in the first, a run-scoring double in the second and an RBI single in the fifth. He scored twice.
The Giants won their ninth in a row overall against Colorado. They also have beaten the Rockies nine straight times at AT&T Park.
Andres Torres hit a two-run single for the Giants, who chased Jeff Francis (1-1) in the second inning for the shortest start of his career. San Francisco had a season-high 16 hits a day after getting 14.
DIAMONDBACKS 10, PIRATES 2
PHOENIX (AP) — A.J. Pollock homered twice, doubled and drove in four runs as Arizona salvaged the finale of its three-game series against Pittsburgh.
Pollock began the day in an 0-for-14 rut. He also made a diving catch in centre field to rob Andrew McCutchen in the first inning.
Wade Miley (2-0) allowed two runs on five hits in 6 2-3 innings.
Jonathan Sanchez (0-2) was charged with nine runs and eight hits in 3 1-3 innings. The last two of those runs came after Sanchez left and reliever Chris Leroux walked two batters, on four pitches each, with the bases loaded in the Diamondbacks' four-run fourth.
PHILLIES 7, METS 3
PHILADELPHIA (AP) — Domonic Brown and Chase Utley homered in a five-run first, Kyle Kendrick threw six effective innings and Philadelphia beat New York.
Pinch-hitter Laynce Nix also went deep for the Phillies, who took two straight from the Mets to earn their first series win of the year.
John Buck homered for the third straight game and Lucas Duda had two solo shots for New York. The Mets set a club record by hitting at least one homer in their first nine games.
Kendrick (1-1) allowed two runs and eight hits to become the first Philadelphia starter other than Cliff Lee to get a win.
Mets starter Jeremy Hefner (0-2) gave up five runs and six hits in three innings.
A rain delay halted the game for 27 minutes in the bottom of the fourth.
DODGERS 4, PADRES 3
SAN DIEGO (AP) — Carl Crawford led off with an opposite-field homer and A.J. Ellis added a two-run shot to back Chad Billingsley's strong season debut and lead Los Angeles over San Diego.
Billingsley (1-0) opened the season on the disabled list after bruising his right index finger during a bunting drill on March 15. He held San Diego to one run and five hits in six innings.
Crawford homered to left field on the second pitch from Eric Stults (1-1). He tripled off the left-field wall in the fifth and scored on Mark Ellis' single through a drawn-in infield to make it 4-1.
Brandon League earned his third save in as many chances, but only after allowing two runs on three hits in the ninth.
San Diego's Nick Hundley had four hits to tie his career high.
NATIONALS 5, WHITE SOX 2
WASHINGTON (AP) — Bryce Harper homered, Ian Desmond had three extra-base hits and Washington beat Chicago to stay unbeaten at home.
In a game that began 16 minutes late because, the Nationals explained, the umpires got stuck in traffic, Washington starter Jordan Zimmermann (2-0) limited the White Sox to two runs and seven hits in seven innings. Both runs scored on groundouts.
Drew Storen pitched the eighth and Rafael Soriano earned his fourth save in five chances.
Danny Espinosa provided his first two RBIs of the season
Harper hit his fourth homer into the second deck leading off the fourth against Gavin Floyd (0-2), who allowed five runs and nine hits in 5 1-3 innings.
Desmond tripled, doubled twice and scored two runs as the reigning NL East champions improved to 5-0 at Nationals Park.