It's the first time a pitcher has been moved to the eighth spot since 2005, but it's not new territory for La Russa, who made the move in 1998 and stuck with it for 76 games from July to September.
"If something's not working, why keep doing the same thing?" the manager asked. "Why not do something different? That's all it is."
The Cardinals have struggled offensively in recent games and have fallen seven games behind Milwaukee in the National League Central just days after beginning to close the gap.
"It's not like we're burning up the league offensively," La Russa said. "We've been erratic offensively for a long time."
The manager likened it to the American League's "double leadoff" strategy, where a more talented hitter gets on base before the top of the order, the players who would be more likely to drive him in.
On Saturday, the ninth hitter was Kennedy, who is hitting .221 this season. He was asked by a reporter if being moved to the last spot was an "ego thing."
"Definitely," he said. "We all have egos. That comes into play."
La Russa said that Kennedy was the first player he talked to about the switch, and he hoped the second baseman would understand, because he has spent time in the AL.
After that he told Pineiro, who was recently acquired by the Cardinals and is making his first start as a Redbird on Saturday night. La Russa said there was no significance to Pineiro being selected as the first pitcher to bat eighth. He has no at-bats this season.
When St. Louis made the move in '98, the team went from six games below .500 to four games above by the end of the season, something La Russa partially attributes to the switch.
"Very few times did I think the pitcher hitting eighth had any kind of detrimental effect on how many runs we scored," he said. "It was either neutral or we felt like we picked up an edge."
He said that the only possible downside was dealing with the distraction it creates, because it is so unprecedented among managers. Dontrelle Willis of the Florida Marlins was the last pitcher to hit higher in the order, doing so for four games in 2005.
La Russa wouldn't commit to doing it for the whole second half, but with a struggling team falling out of contention, he knew he had to do something.
That led him to the same thought he had nine years ago when he decided to make the switch.
"If this improves our chances today," he said. "I don't want to wait."