ST. LOUIS -- Cincinnati Reds right fielder Steve Selsky didn't know if he experienced a five-hit game prior to Monday night.

"That's a great question," he said, grinning.

Selsky and his teammates sure didn't have a hard time figuring out St. Louis Cardinals pitching.

Banging out 22 hits in a game for the first time since 2003 and scoring its most runs in a game this year, Cincinnati led 10-0 before the fourth inning was over and cruised to a 15-2 blowout that leaves St. Louis in need of help to earn a sixth straight playoff berth.

Selsky led the hit parade by going 5-for-5, including a solo homer in the second, and driving in four runs. Left fielder Adam Duvall went 4-for-6 with two homers, his third two-homer game of the year, and five RBIs to give him 100 for the season.

Second baseman Brandon Phillips also collected four hits, the 14th time in his career he's accomplished that feat, and knocked in a pair of runs as the Reds (66-90) became the first team since May 2014 to bang out 20 hits in a game against the Cardinals.

"You don't get 22 hits and 15 runs in a game often," Cincinnati manager Bryan Price said. "That just doesn't happen for anybody, so you relish those games when they come."

The storyline prior to this game was St. Louis' opportunity to tie the idle San Francisco Giants for the second National League Wild Card spot. But Jaime Garcia (10-13), making his first start since Sept. 13, put the Cardinals in a quick hole by yielding back-to-back two-out homers in the first to Joey Votto and Duvall.

Cardinals manager Mike Matheny opted for the quick hook and brought Michael Wacha in to open the second, but Selsky walloped his second pitch over the wall in right-center for a quick 3-0 lead.

The Reds turned the fourth frame into a round of batting practice, peppering Wacha and Luke Weaver for eight hits -- all singles -- and seven runs. Selsky and Tucker Barnhart each stroked two hits in the inning as Cincinnati ended the game's competitive phase by grabbing a 10-0 lead.

Duvall mashed his second homer of the night in the fifth, a three-run shot to left that gave him 33 for the year. Not bad work for a guy who many pigeon-holed as a platoon player when the Reds broke spring training.

"That's one of the goals that I had, looking at the end of the season," Duvall said of his 100 RBIs. "It was good to get that mark. I've had a lot of chances to drive in runs because the guys in front of me have gotten on. It's gratifying to show people that I can do it at this level."

Not to be outdone, Reds rookie starter Tim Adelman (3-4) worked seven solid innings, giving up four hits and two runs with no walks and four strikeouts in the longest outing of his career.

It was such a blowout that Matheny decided to rest catcher Yadier Molina after his sacrifice fly in the fourth put St. Louis on the board. By game's end, the crowd and the names on the field resembled spring training more than a regular season game.

"You never want to be embarrassed, and that's an embarrassing loss," Matheny said.

In dropping to 81-75, the Cardinals fell a game behind San Francisco while staying 1 1/2 games behind the New York Mets for the first wild card. New York fell 7-3 in Miami.

While St. Louis endured its worst loss of the year, the Reds unleashed a barrage more suited for the Big Red Machine of the 1970s instead of the team which is likely headed for a last place finish in the NL Central.

"For the offense to string together hits the way they did against a team fighting for a playoff spot was huge," Adleman said.

NOTES: St. Louis SS Aledmys Diaz traveled to Miami Monday to grieve with the family of Jose Fernandez, the Marlins' All-Star pitcher who died in a boating accident early Sunday morning. Diaz flew back to St. Louis late Monday afternoon to be available for the game. ... Cincinnati placed SS Zack Cozart (knee) on the 15-day DL, retroactive to Sept. 16. Cozart batted .252 with 16 homers and 50 RBI this year. ... Cardinals INF Matt Carpenter (hand), mired in a 1-for-16 slump, didn't start Monday night as Greg Garcia got the call at 2B.