The St. Louis Cardinals hoped their come-from behind win on Wednesday over the Chicago Cubs would get them back on track.
Instead, they followed with their most one-sided defeat this season.
St. Louis opened its longest trip this season -- 10 games in 11 days -- with its fourth loss in five games, including a 9-0 defeat to the Cubs on Monday.
Reds star Joey Votto doubled and singled, driving in a run and scoring one, a day after his tantrum at home plate following an ejection.
Garcia (8-5) lasted a season-low 4 1/3 innings and gave up six runs. He had been 5-0 in seven starts since losing to the Reds on July 28.
"Definitely not a good one," Garcia said. "There are no excuses. I've got to do a better job the next time."
John Lamb (1-3), one of three left-handers acquired from Kansas City for Johnny Cueto in late July, shook off control problems for his first major league win. He walked six, struck out six and gave up three hits in five innings.
"It was a crazy game," Lamb said.
Four relievers combined to complete St. Louis's 12th shutout loss this year, matching last season's total.
The Reds scored their first two runs on groundouts. Lamb got his first career RBI in the second and Phillips made it 2-0 in the third.
Cincinnati chased Garcia in a four-run fifth that included RBI doubles by Votto and Frazier. Phillips and Bruce each had a sacrifice fly.
Votto's double into the left field corner came on a 3-2 pitch after he fell behind 0-2 and was sent sprawling by a high-and-tight fastball.
"He's locked in right now," manager Mike Matheny said of Votto. "That kind of changed the game a little bit."
Phillips hit 12th homer, a leadoff shot in a three-run seventh. Right fielder Jason Heyward almost made a leaping catch, but he couldn't keep the ball in his glove.
Frazier added his 32nd homer, a two-run line drive in the eighth.
"It's a great feeling, but you have to stay on an even keel," Frazier said.
St. Louis 1B Matt Adams made his first appearance after missing 91 games with a quad injury as a pinch-hitter in the ninth and singled. "Everybody was happy to see him back and active," manager Mike Matheny said. "We were excited to get him in there."
Todd Frazier's fifth-inning double was his NL-leading 40th this season, making him just the fourth player in Reds history with at least 40 doubles and 30 home runs in the same season. Frank Robinson (1962), Dave Parker (1985) and Jay Bruce (2013) are the other three.
Cardinals: OF Randal Grichuk took the day off from throwing as he continues to rehab his inflamed right elbow. The Reds have right-handers scheduled to start the final three games of the series, which means the right-handed hitting Grichuk might not start all weekend.
Reds: C Brayan Pena will be "limited for a couple of days," manager Bryan Price said. Pena strained his right hamstring legging out a pinch-hit double in the eighth inning of Cincinnati's 5-4 loss to Pittsburgh on Wednesday.
Cardinals: RHP John Lackey (11-9, 2.90) scheduled to start Friday, a year and a day after he was ejected in the third inning for arguing balls and strikes against the Reds in Cincinnati.
Reds: RHP Michael Lorenzen (4-8, 5.54) is coming off his first win in his last 10 starts.
Link to box score: Cincinnati (58-81) 11, St. Louis (88-52) 0