Santana is 2-for-20 in five games since his return. Santana was hitless in three games before his concussion, and has seen his average drop from .262 to .229. Acta said the week-long layoff was a factor in Santana's struggles early in his return.
"But that doesn't mean it's the reason why he's where he's at," Acta said Saturday. "To him, it's going to continue to be a battle, a battle he continues work with his body movement at the plate."
Santana will play first base on Sunday against the Cardinals, and Lou Marson will relieve him behind the plate.
The switch-hitting Santana hasn't had much more success at either side of the plate this season. He's batting .217 against lefties and .235 against right-handers this season. Acta said the repercussions of Santana's concussion seem to have affected the catcher batting right and left.
The manager sites the leg kick in Santana's swing as a reason for his slow progress.
"It's a high leg kick just like every hitter that does those things, it's a lot of rhythm," Acta said. "Guys that rely on that have a tendency to be up and down at times because that's what pitchers try to do. Less is more. The less body movement you have at the plate, the better chance you have to keep those eyes quiet."