The barrage was led by a couple of Houston's "youth movement" players, second baseman Jose Altuve and first baseman Chris Carter.
Altuve, who hit .290 in 147 games last season, was 4-for-6 against the Mariners, stroking a pair of singles, a double and his first homer of the season, a two-out, two-run, fourth inning shot, raising his batting average to a sharp .353. Altuve drove in four runs from the leadoff spot.
Carter belted a pair of solo homers and had two singles in six at-bats, driving in three runs. Carter's homers were his first of the season. He socked 16 in 67 games with Oakland last year and was traded to the Astros during the off-season.
St. Louis isn't planning on letting the Reds forge a big lead in the NL Central.
After losing the opener of their three-game set in Cincy, the Cards rode the arm of Lance Lynn to a 6-1 victory, evening their record at 4-4, while cutting the Reds' division lead to one game.
Lynn allowed one earned run on four hits over six innings with one walk. He struck out 10 for his first win of the season (1-0), throwing 101 pitches before departing the mound.
A trio of St. Louis relievers finished up, each working an inning, setting down the Reds on one hit.
Homer Bailey will start Wednesday's rubber game against Cardinal starter, Jake Westbrook, at 1:45 EDT in St. Louis.