Sellers has been playing in increasing pain and the injury was diagnosed through an MRI Thursday. Manager Don Mattingly said the club is optimistic that anti-inflammatory medication and strengthening exercises will have Sellers able to return in the minimum 15 days.
Sellers said he had a back condition in high school, but nothing like what locked up earlier this week. He said surgery is not currently being considered.
"Back issues are no joke and you could be out a long time," he said. "We have to stay on top of it. Hopefully I'll get on a good program and avoid surgery."
Sellers said he was really banged up in the days after his May 15 catch of the D-backs' Miguel Montero's foul pop-up, in which he slammed into and sailed over the auxiliary scoreboard, landing on his back between two aisles of seats.
"It could be an aftershock of that play," he said. "Going into the stands took more of a toll on my body than I thought. I started to feel a tingle down the right side."
Mattingly's career was curtailed by back problems.
"When the bulging disk hits the nerve, I've been through that and it gets in that area and it's hard to compete," he said. "We feel if we get it calmed down it will be just a couple weeks. Once you get it off the nerve it feels normal."
To replace Sellers, utilityman Jerry Hairston was activated from the 15-day disabled list.