St. Louis tied a season-high with its sixth straight win.
Kansas City has lost four in a row and six of seven.
St. Louis climbed within one game of the first-place Chicago Cubs in the NL Central.
Fowler broke a 3-3 tie in the seventh inning with his 15th homer of the season. He ripped the first pitch from Neftali Feliz 404 feet for his third career slam.
Lorenzo Cain had four hits for the Royals, who lost all four games in the four-game, home-and-home set.
Fowler also ripped a run-scoring double to trigger a three-run outburst in the sixth inning that helped erase a 3-0 deficit.
Trevor Rosenthal recorded four outs to pick up his 10th save in 12 opportunities.
Pinch-hitter Brandon Moss brought the Royals within 7-5 with a two-run, bases-loaded double in the eighth that came within a foot of clearing the wall. Whit Merrifield followed with a sacrifice fly. But Rosenthal got Cain to fly out with the tying run on third.
St. Louis has scored 54 runs during the six-game streak.
Tyler Lyons (1-0) picked up the win in relief of Lance Lynn, who gave up two earned runs in six innings.
Mike Minor (5-4) took the loss.
Melky Cabrera gave the Royals a 3-0 lead with a two-run triple in the fifth.
Kansas City starter Jason Hammel gave up two earned runs and three hits over five-plus innings. He has allowed three earned runs or less in each of his last seven starts.
GRAND SLAM UP
The Cardinals recorded grand slams in back-to-back games for the first time since Aug. 31-Sept. 1, 2011. Yadier Molina hit a slam in Wednesday’s 8-5 win.
Jake Westbrook and Albert Pujols did the trick in 2011.
The rally cat has apparently disappeared.
The feline ran onto the field in the sixth inning of the Cardinals’ 8-5 win over Kansas City on Wednesday night.
Molina hit a grand slam on the very next pitch after the delay.
The kitten was taken off the field by a member of the Cardinals grounds crew, who set the animal outside the stadium. The cat was picked up by a female fan, who intended to adopt it and take it home. But the cat jumped from her grasp a couple of blocks from the stadium and has not been seen since.
EXTRA TOUGH ESCOBAR
Kansas City INF Alcides Escobar made his 285th consecutive start on Thursday. It is the longest streak by a shortstop since Baltimore’s Cal Ripken Jr. started a record 2,216 consecutive games from 1982-1996.
Royals: RHP Trevor Cahill was placed on the 10-day disabled list with right shoulder soreness. RHP Kevin McCarthy has been called up from Triple-A Omaha. McCarthy is 1-0 with a 2.14 ERA in 16 appearances over two stints with Kansas City this season.
Royals: LHP Danny Duffy (7-7, 3.48) will face RHP Reynaldo Lopez (0-0, 0.00) in the first of a three-game series against the White Sox on Friday in Chicago. Duffy is 0-2 with an 11.17 ERA in two starts against Chicago this season.
Cardinals: RHP Adam Wainwright (11-5, 5.00) takes on RHP Mike Foltynewicz (10-6, 3.94) in the opener of a three-game set against Atlanta in St. Louis on Friday.
— Associated Press —