The Cardinals evened the score in the very next half inning on a solo home run from Matt Adams -- his 15th of the year -- then took a two-run lead on a double into the left-center field gap off the bat of pitcher Adam Wainwright.
St. Louis tacked on another pair of runs in the top of the fourth on a two-run shot from Jedd Gryorko that traveled an estimated 452 feet, landing just shy of the rockpile in center field.
Daniel Descalso's career-high-extending eighth home run of the season brought the Rockies to within three runs at 5-2 but the Cardinals counterpunched hard, knocking De La Rosa out of the game and potentially ending his Rockies' career on a sour note.
They scored three times in the fifth, again Wainwright getting in on the action with a two-run base hit before the inning closed with the Cardinals up 8-2.
De La Rosa's final line -- in perhaps his final game for Colorado: 4.2 IP, 7 H, 8 ER, 3 BB, 8 K.
Blackmon made it 8-3 in the bottom fifth with his 28th home run of the season. The blast off the right-field foul pole also brought Blackmon's 2016 RBI total to 75, tying Eric Young for the franchise record.
But the Cardinals couldn't even let the Rockies inch back in as the team went back in forth over the next few inning. Brandon Moss scored Gyorko on a sac fly in the sixth. Gerardo Parra hit a solo home run in the bottom of the inning. Then Jeremy Hazelbaker drove in Randal Grichuk to knock Eddie Butler out of the game in the seventh.
The Rockies got a final token run in the bottom of the ninth on an RBI single from Raimel Tapia, driving in Descalso, and that ended the scoring on the night with the Rockies down 10-5 and never really a threat to win this one.
By the Numbers
75 - Blackmon's home run in the fifth ties him with Eric Young for the all-time record for RBI out of the lead off spot.
36 - DJ LeMahieu extended his career-high on-base streak to 36 games.
The Rockies will try to avoid the sweep tomorrow afternoon in the final game against the Cardinals. German Marquez, the 21-year-old rookie, will get the first start of his MLB career against Luke Weaver. First pitch is at 1:10 MST.