With two outs in the ninth inning on Friday, a line drive off the bat of Nick Markakis sent Reddick sprinting toward the wall.
After leaping to secure the catch, Reddick slammed into the lightly-padded concrete wall, sending a "shock" up his back and knocking the wind out of him.
"It was pretty scary," Reddick said. "Looking back, it didn't look as bad as it felt. Just never been scared like that before."
After spending a few minutes face-up on the warning track with his eyes closed -- he said he was playing it safe, given that the game was over and there was no rush to get back up -- Reddick regained normal breathing and was carted to the clubhouse.
Reddick iced the bruised area behind his right shoulder, and said Saturday there was no bruising.
"It scared us all for a bit, but he came out of it better than I thought today," A's manager Bob Melvin said. "But we're going to be careful with him, at least at the start today. He might be able to pinch-hit."
Reddick participated in batting practice and fielding drills as normal on Saturday, even making time to try on his new full-body Spiderman costume in the clubhouse.
While Melvin and trainer Nick Paparesta said Reddick would be evaluated again before a decision is made about Sunday's lineup, all three seemed optimistic that he'd be ready to go.
"If everything goes well today, we'd look to get him back out there again tomorrow," Paparesta said.
"Back out there tomorrow, starting in the outfield," Reddick said. "I'll do it again if I have to catch the ball."