The Cardinals moved back into first place in the NL Central, one-half game ahead of the Chicago Cubs, who lost to Washington earlier Friday. The Cardinals have won five of six and 11 of 14.
The Rockies lost for the fourth time in five games and fell to 18-37 since June 21.
Flaherty (8-6) allowed three hits, struck out nine and walked one. He has allowed one earned run in his past 34 innings and has won four straight decisions. He hasn't lost since July 7, when he allowed just two hits at San Francisco but St. Louis fell 1-0.
Peter Lambert (2-4) lasted 4 1/3 innings and gave up six hits and four runs (two earned).
Ozuna's 24th homer of the season over the Colorado bullpen in left field gave St. Louis a 2-0 lead in the first. He also doubled in Paul Goldschmidt in the sixth and later scored on a single from Paul DeJong.
The homer came after one of several miscues by the Rockies. Kolten Wong reached on an error by second baseman Ryan McMahon and Ozuna's blast came one out later, accounting for two of the four unearned runs surrendered by Colorado.
Lambert plunked Wong in the fourth with the bases loaded to give the Cardinals a 3-0 lead.
The Cardinals broke the game open in the fifth on a swinging bunt by Harrison Bader and a bad throw from reliever Wes Parsons, who fired the ball down the right-field line. That allowed Yadier Molina and Tommy Edman to score and Bader to reach third. He scored on Flaherty's sacrifice fly to center as St. Louis went up 6-0.
The Rockies scored three times in the ninth off John Gant.
TAKING A WALK
Since returning to the Cardinals following a 16-game stint at Triple-A Memphis to work on his hitting, Bader is 2-for-9 but has drawn six walks, including one Friday.
DEFLECTION
Nolan Arenado and Molina got hurt by the same Flaherty pitch. The throw first hit Arenado near his right wrist before ricocheting off Molina's mask. Both players required attention from their respective trainers but stayed in the game.
Molina finished with three singles, and Arenado reached base in all four of his plate appearances.
HALL OF FAME
The Cardinals on Saturday will induct three players into the team's hall of fame. This year's honorees are third baseman Scott Rolen (who played in St. Louis from 2002-07), right-hander Jason Isringhausen (2002-08), and right-hander Mort Cooper (1938-45). Each year, fans vote for two modern-era players and a panel selects a veteran player.
TRAINER'S ROOM
Rockies: RHP Jon Gray (fracture) had two screws inserted into his left foot Friday. ... RHP Scott Oberg had "arterial repair" in St. Louis, Manager Bud Black said. Oberg is out for the season because of a blood clot in his right arm.
Cardinals: OF Tyler O'Neill (left wrist strain) was scheduled to play Friday night for Triple-A Memphis in the second game of his rehab assignment. He was 1-3 on Wednesday for the Redbirds.
UP NEXT
Rockies: RHP Chi Chi Gonzalez (0-4, 5.87 ERA), who pitches Saturday, is looking for his first win since September 22, 2015, while with the Texas Rangers. He lost both decisions in 2016, missed the entire 2017 season after Tommy John surgery and didn't return to the majors until June 25. The Rockies have lost all six games in which he has appeared.
Cardinals: RHP Dakota Hudson (12-6, 3.63) goes for his third consecutive win. He was pulled after throwing 6 2/3 hitless innings against Milwaukee on Monday.
