"The night really started with Johnny," teammate Brandon Phillips said. "He pitched a lights-out game and we were behind him, catching the ball and hitting where they weren't."
Cardinals starter Kyle Lohse (4-4) was taken out with none out in the third inning complaining of tightness and pain in his right forearm. Lohse said cramping and a burning sensation, which forced him to miss a turn in the rotation, returned after he made a diving stop to glove Cueto's bunt for a hit to start the third.
He left after falling behind 3-1 in the count against the next batter, Jerry Hairston Jr.
"I was trying to make a play and just threw in an awkward motion that definitely re-aggravated it," Lohse said. "After that, I obviously couldn't pitch."
Lohse was to undergo an MRI exam later Wednesday night.
"It's hard to force yourself to release it," Lohse said. "It's hard to do the proper things that you need to do to get the location and everything else. I felt like I was doing all right up until that point."
Cueto's string of long starts included a seven-inning stint in which he gave up one run in a 6-4 victory over St. Louis on May 8 in Cincinnati. Despite going deep into every game he had been 0-2 in his previous three starts.
He walked none for the third time and lowered his ERA to 2.43, among the league leaders.
"I was aggressive with all my pitches," Cueto said through an interpreter. "That was the big difference."
Nix homered in the second for the Reds' first run and added a three-run shot, his sixth of the season, off Chris Perez in the eighth for a 7-1 cushion. He also made an outstanding leaping catch to rob Ryan Ludwick of extra bases and an RBI in the sixth.
"That kept them from getting a rally going," Nix said. "That might have been as important as the second homer."
Phillips was 3-for-5 with his 10th homer in the ninth, and stole second and third after his RBI single in the third. Those were his first steals off strong-armed catcher Yadier Molina, although he said he was running off reliever Blaine Boyer.
"That was the highlight of my day, honestly," Phillips said. "You don't run off that dude. I was so glad [Boyer] had a nice little leg kick, and I made it."
Cueto ended the Reds' string of allowing a first-inning run in six straight games with the help of a leaping catch by Hairston at third to rob leadoff hitter Skip Schumaker. Before pinch hitter Colby Rasmus and Ryan hit back-to-back doubles with one out in the seventh, the Cardinals had only two runners in scoring position.
Cueto's leadoff bunt single, his third bunt hit of the year and fourth hit overall, ignited a two-run third with both runs unearned due to third baseman Joe Thurston's fielding error.
Boyer worked allowed one earned run in five innings, the longest by a Cardinal reliever since Kip Wells also went five innings July 3, 2007 against Arizona.
Cardinals manager Tony La Russa has sued Twitter after an unknown user created an account in his name and pretended to post updates as him. ... Nix has four career multihomer games, the last on May 12, 2004 against the Yankees. ... Hairston batted leadoff for the third time for the Reds in place of Willy Taveras, still bothered by a tight right hamstring. ... The Reds are likely to recall LHP Matt Maloney from Triple-A Nashville to start Saturday in place of injured Edinson Volquez. Maloney threw a shutout on Monday. ... Molina picked off Chris Dickerson in the first, his fourth of the season and 30th of his career. ... The Reds' Jay Bruce was back in the cleanup spot after batting second one game. The shakeup didn't work -- he was 0 for 4 with a walk that extended his slump to 1 for 24 and dropped his average to .216.