The Reds and Cardinals were tied at 1-1 entering the inning, before DeJong's two-run shot granted the home team its final 3-1 advantage Thursday at Busch Stadium in St. Louis.
Reds reliever Michael Lorenzen came out of the bullpen to take the mound in the bottom of the seventh inning. He allowed a leadoff single to Yairo Munoz before striking out Cardinals star Matt Carpenter. DeJong then stepped into the box to face the Reds righty.
Lorenzen worked to an even 2-2 count against the Cardinals shortstop, before issuing an 86.8 mph changeup for his fifth offering of the exchange. DeJong belted the middle-of-the-plate offering over the left field fence for his ninth home run of the season.
The two-run, 388-foot shot had an exit velocity of 105 mph and a launch angle of 23 degrees, according to Statcast.
"[I] personally needed it, and our team needed it, so I was just happy to come through for the group," DeJong told reporters, according to MLB.com. "May was a tough month. It takes some mental toughness to overcome things like that. Being confident in myself to go out there and when that shows up in the middle, I'm ready to swing, ready to hit. Today was good for that, for my confidence."
Carpenter helped the Cardinals draw first blood with an RBI single in the third inning. The Reds tied the score on a Tucker Barnhart sacrifice fly in the top of the next inning. Marcell Ozuna was 2-for-4 with a strikeout in the win. DeJong was 1-for-4 with two RBIs, a run scored and a strikeout for the Cardinals.
Cardinals starter Dakota Hudson allowed five hits and one run in 6.1 innings, but did not earn the win. Relief pitcher John Gant moved to 5-0 on the season, limited the Reds with 1.1 shutout innings.