The Cardinals now boast a 25-24 record on the season, while the Royals dropped to 17-32 with one of the worst records in baseball.
Right fielder Jorge Soler provided the power in the Royals' series-opening 8-2 win on Wednesday afternoon at Busch Stadium in St. Louis. The Cardinals hit four home runs in the second game, winning 10-3 on Wednesday night.
Hunter Dozier put the Royals up 1-0 with a second inning sacrifice fly, before Kansas City erupted for a six-run third inning in the first game.
Soler's three-run smash off of Cardinals starter Michael Wacha was the highlight of the inning. The long ball traveled 411 feet and had an exit velocity of 108 mph, according to Statcast.
Abalberto Mondesi drove in Nicky Lopez with a seventh inning triple to give the Royals an 8-0 lead. Marcell Ozuna plated the Cardinals' lone runs with a two-run double in the eighth inning of the loss.
Soler went 1-for-4 with three RBIs, a run scored and a strikeout in the win. Mondesi was 2-for-5 with two RBIs, a run scored and a strikeout for the Royals.
Royals starter Brad Keller improved to 3-5 on the season after allowing two hits and two runs in seven innings.
The Cardinals pounced early in the nightcap. Ozuna hit his 14th home run of the season in the bottom of the first inning, smacking a three-run bomb off of Royals starter Homer Bailey. Matt Carpenter followed with a two-run bomb in the next inning, giving the Cardinals a 5-0 edge.
Mondesi and Soler each hit RBI singles in the third inning, cutting the Cardinals' lead to 5-2. Royals slugger Hunter Dozier homered in the fifth frame for Kansas City's final run of the game.
Dexter Fowler hit the Cardinals' third homer of the game in the sixth inning. The Cardinals added four more runs in the next frame to take control of the game. Yadier Molina began the seventh inning with an RBI single. Kolten Wong provided the biggest blow of the inning with a three-run homer off of Royals reliever Scott Barlow.
"It's big," Ozuna told reporters, according to MLB.com. "After we lost the game before, we got an early shot and we put some [runs] on the board, and that's pretty impressive."