Hernandez went 3-for-3, going deep in the third and fifth innings, and Brandon Phillips added a solo shot among his three RBI for the Reds, who clinched a three-game series against St. Louis.
Cueto (2-0), making his second start of the season after being out with right biceps soreness, was tough, allowing no earned runs on only three hits and two walks, and fanning five.
Cards starter Kyle McClellan (5-1), meanwhile, surrendered four runs on seven hits over six frames, taking his first loss since being promoted from the bullpen to replace the injured Adam Wainwright.
Jon Jay hit a three-run homer to provide the Cardinals' offense.
NBC reportedly holds celebs hostage to Jimmy Fallon's show
Ray Liotta sues skin care company over use of likeness