Theriot responded exceptionally well to his new role and went 4-for-5 with a pair of doubles, three RBIs and a run scored in the Cardinals' 13-5 win over the Cubs. He's excelled against his former team so far in this series, going 6-for-7 with six RBIs in two games.
"This is more like him, he's spraying the ball all over [the field]," said Cardinals manager Tony La Russa.
Theriot also played three innings at second base during Friday's 9-2 win against the Cubs.
"It was kind of fun, actually," Theriot said. "It's something new. What we do is such a repetitive thing. You eat the same stuff, you come to the yard the same time, you take the same amount of swings in the cage, you play the same position. So when you can do something a little different like that, [it's] cool."
Theriot pinch-hit for Corey Patterson in the sixth inning on Friday and broke out of a 2-for-34 slump with a two-run double.
Theriot, who was the Cardinals' Opening Day starter at shortstop, welcomed the move to second base because it lightens the load on his sore shoulder. He said the soreness came from taking extra cuts in the batting cage to straighten out his swing.
"It's a little dinged up," Theriot said. "[Thursday] night, I had some long throws and some tough throws and didn't feel it at all. Honestly, it's just from swinging too much."
La Russa elected to start Daniel Descalso at shortstop on Saturday, moving Theriot to second in part to protect his shoulder.
"That factors into it, made it kind of easy to do," La Russa said.