Reddick is considered day to day after having the wind knocked out of him on impact. He showed no signs of a concussion or head injury, and manager Bob Melvin said Reddick is not expected to undergo further testing.
"He took a pretty good blow," Melvin said. "We'll see where we're at with him tomorrow. If we need to give him a day, we'll give him a day."
The A's right fielder crumpled to the warning track after securing the final out of Oakland's 14-9 win in Baltimore with a leaping catch, staying down for several minutes.
"He stayed down for so long because he had the wind knocked out of himself," Paparesta said. "That was the reason for the length of being down. Then, when he got up, he felt his upper shoulder being sore."
Reddick lay face-up, at times rubbing his head as team trainers and Melvin rushed out to check on him. His teammates anxiously looked on from the mound area while trainers assessed him, ultimately finding nothing but a small bruise behind his right shoulder.
"We actually made him laugh a couple times," Melvin said. "You're trying to get a reaction out of him just to see if he's aware of what you're saying. He's a tough kid, that's a hell of a play. Especially with the magnitude, to seal the last out."
After getting to his feet, Reddick took a seat on a cart and was driven to the A's clubhouse.
"He was walking around after," Melvin said. "It stunned him, you could tell he was a little bit stunned, and therefore you're thinking maybe it was something to the head. But I think just the collision with his back and knocking the wind out of him, it stunned him and took him a while to get up and have all of his actions about him."
Reddick has been one of the A's most valuable players this season, hitting .271 with a team-high 22 home runs and 49 RBIs.
"That's something we don't want to see," pitcher Jarrod Parker said of Reddick's injury. "He made a heck of a play, and obviously we'll worry about him. He'll probably be a little sore tomorrow."
Greg Luca is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.