Villanueva entered the game in the bottom of the 10th inning with no safety net behind him. St. Louis had already used six relief pitchers, so Villanueva was the last man standing.
"There was no pitch count in mind," the 31-year-old right-hander said with a smile. "You can't really be thinking about that when the game is on the line. But there is a little anxiety there."
There was no shortage of anxiety in the 10th when Villanueva faced the top of the Cincinnati order with one out and two runners on base. Billy Hamilton, Joey Votto and Todd Frazier came into the game batting a combined .310.
Hamilton worked the count full before taking a called third strike, Votto walked on four pitches, and Villanueva struck out Frazier on four pitches, the last one a slider.
"You try to make Votto get himself out, which is not disrespecting Frazier at all," Villanueva said. "Frazier is more aggressive and Votto is more selective, so you take your chances with Frazier."
The Reds put two on base in the 11th as well, but Villanueva got Zack Cozart to ground into a forceout to end the game.
Carpenter came up in the top of the 11th, worked the count full, then turned on a waist-high fastball from Kevin Gregg and drove it into the center-field seats to give St. Louis the lead for good.
"We have talked about him using his power," Cardinals manager Mike Matheny said of the 29-year old third baseman.
Carpenter said striking a balance between using that power and maintaining a leadoff hitter mindset can be a tough task.
"It comes down to picking your spots," Carpenter said. "When is the opportunity to take a more aggressive approach to an at-bat? It's all a learning process."
Worth noting: Matheny confirmed that catcher Tony Cruz will rejoin the Cardinals for Monday's home opener. Cruz has been in Florida on paternity leave since Friday.
Andy Call is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.