"It was great," Reds manager Bryan Price said. "Every time one of the guys came to the dugout, I said, 'That's good timing.' We're not down, 7-1, when someone hits a solo shot. These were impactful homers."
Jay Bruce had two of the long balls and three RBIs, while Todd Frazier and Devin Mesoraco also went deep.
"Obviously every win you get is good," Bruce said. "To get some cushion for the pitchers there and end the final road trip of the year on a good note is something we can take a positive out of, go home and finish strong."
Held to four runs over a five-game stretch on the trip at one point, Cincinnati scored 11 runs in its last two games.
With losses on Friday and Saturday, the Reds still couldn't change the fact they have won only one of their last 22 series at Busch Stadium since August 2006, including the last eight in a row. The nine-game road trip concluded with a 2-7 record, while the 72-84 Reds avoided their 50th road loss. They also improved to 11-20 on Sunday nights.
The Cardinals, who had already clinched a playoff spot earlier in the day with a Brewers loss to the Pirates, are still trying to lock down the National League Central title. Playing the spoiler role was secondary for Price.
"We'd lost every game but one on this trip," Price said. "Winning a game -- it didn't matter who it was against -- was first and foremost."
Overcoming a calf cramp, Reds starter Alfredo Simon worked his third straight quality start as he seems to be finishing strong after several poor starts following his All-Star Game appearance. Simon allowed two earned runs and seven hits over six innings, with two walks and three strikeouts. With one start left in his season, he is 15-10 with a 3.34 ERA in a career-high 191 1/3 innings -- but 3-7 after the break.
Cardinals starter Lance Lynn kept the Reds hitless for the first 3 2/3 innings before Bruce lifted an 0-1 pitch to right field and gave his team a 1-0 lead.
There wasn't another Reds hit until one out in the sixth, when Frazier hit a 2-0 Lynn pitch to left field for his 27th homer and a 2-1 Cincinnati lead. It was the first time since Sept. 6 that the Reds had multiple home runs in a game. Two batters later, Brandon Phillips hit a two-out double to left field and then scored on a Bruce RBI single to left.
Simon, who gave up a run in the fifth, allowed back-to-back one-out doubles to Yadier Molina and Randal Grichuk in the bottom of the sixth that put St. Louis back to one run down.
The gap widened in the eighth when the Cardinals' bullpen faltered. Lefty Kevin Siegrist walked his first two batters, and his replacement, righty Sam Tuivailala, surrendered a three-run homer to left field by Mesoraco. It was Mesoraco's 24th homer of the season. Two batters later, with one out, Bruce went deep again for his 18th homer, sending a 2-2 pitch to right field.
"The Cardinals are hard to score runs against," Bruce said. "Lance Lynn has done a very nice job all year. To be able to get to him a little bit and continue to keep our foot on the gas and score some runs to kind of ease into a win there, it's nice."