Ray was removed from Wednesday's start at Colorado while warming up before the start of the third inning. He gave up one run and one hit, and the Diamondbacks went on to a 7-6 loss.
The 27-year-old Ray is 10-7 with a 3.99 ERA. He ranks among the NL leaders with 187 strikeouts in 142 innings.
Ray had an MRI that showed nothing irregular in his back. He missed about two months last season because of an oblique injury.
"He's had problems with his oblique in the past and those things go through your head," manager Torey Lovullo said. "It's quite a relief. We had to make the right decision for him moving forward instead of fast-forwarding things.
"We just need to be smart and mindful to get out ahead of it so he can remain healthy the rest of the year. The comforting factor for me is that he is going to be 100% the rest of the year."
With off days, Ray would miss only one start if he is able to return the first day eligible, on Aug. 25.
Duplantier has made three starts for Arizona this season.