Zobrist tweaked his lower back in the weight room on Wednesday, causing him to miss the first two full-squad workouts.
Rays manager Joe Maddon seemed encouraged by Zobrist's progress after meeting with him Friday morning.
"He said he felt better and [his back] was getting looser," Maddon said. "We still don't have a final moment yet, but he felt better than he did yesterday, and that's always a good sign.
"It's unfortunate that it happened at all. But all the signs are good. Just get it out of the way and move forward. But you'd rather not go through that right now."
Bill Chastain is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.