Matt Adams' second homer sent St. Louis to a 5-4 victory over the Cincinnati Reds in 16 innings on Wednesday night, protecting the Cardinals' hold on second place in the NL Central.
Adams broke an 0-for-17 slump by connecting in the 14th.
After St. Louis let that lead get away, he homered again off Logan Ondrusek (3-1), ending the Reds' longest game of the season.
The Cardinals had dropped the first two games in the series, letting the Reds get within a game and a half for second place.
They finish their season series on Thursday. St. Louis leads it 11-8.
Carlos Martinez (2-1) escaped a threat in the 15th, when Shin-Soo Choo reached third with two outs but was caught in a rundown.