Spring Training: Schedule | Tickets | More info
Once O'Conner reached camp, the source of the pain was diagnosed. He has since been on limited activity.
"I've been feeling a little better the past couple of days," O'Conner said. "I might start doing a little more activity, but it's still mostly rest."
O'Conner said he is scheduled to visit a doctor on Monday.
"Pretty unfortunate," Rays manager Kevin Cash said. "I highly doubt we'll see him at all in this camp. He's going to kind of be just hanging out in the training room and doing a lot of treatment and going from there.
"Disappointing for anybody, especially a young player that's coming in. He does a lot of things. You hear about a lot of good things he's capable of doing. This is an opportunity to kind of showcase some of that. A little unfortunate, but we'll get him better and get him on the field."
Because O'Conner's activity will be limited for at least the first several weeks of Spring Training, the Rays have added catcher Mayo Acosta to their spring camp as a non-roster invitee. Acosta is available to help with the catching duties. Otherwise, he would have reported to Minor League camp.
O'Conner is ranked by MLBPipeline.com as the Rays' No. 8 prospect. He spent 2015 at Double-A Montgomery, where he hit .231 with nine home runs and 53 RBIs.
O'Conner managed a smile when asked if he'll make the 16-hour drive from his home to Spring Training next season.
"I think I'll fly from now on," he said.
Bill Chastain is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.