St. Louis, which came into the contest with a two-game lead over the Los Angeles Dodgers for the final National League wild card spot, landed in the post-season when the Dodgers fell to San Francisco Tuesday.
Latos (14-4) extended his unbeaten streak to seven starts, holding St. Louis to one run on four hits over five full frames. The right-hander issued one walk and struck out four.
Sam LeCure, Sean Marshall and Jonathan Broxton teamed up for three scoreless relief innings and Aroldis Chapman racked up his 38th save for the National League Central champion Reds, who evened their season-ending three-game series.
Cards starter Chris Carpenter (0-2) was tagged with the loss, surrendering three runs on seven hits over six innings.
Matt Holliday drove in the only run for St. Louis, which will face Atlanta in a one-game wild card series Friday.