The right-hander had an MRI on Monday and was examined by team physician Gary Waslewski. The team declined to say what the MRI revealed other than "elbow inflammation."
"He didn't really tell me much," Miller said of what he heard Monday from the doctor. "Just kind of looked at the MRI a little bit and saw something was there -- some inflammation and stuff. I'm going to get a second opinion tomorrow and go from there. Not a lot of specifics. I just know that something is not right."
If there is a tear in the ulnar collateral ligament that requires Tommy John surgery, Miller would miss the rest of the 2017 season and likely good portion of '18 as well.
It's also possible that another form of treatment could be recommended depending on what the doctors are seeing on the MRI.
"I guess there's some kind of chance, but I don't know too much right now," Miller said when asked if surgery was a possibility. "I'll know more tomorrow for sure. Obviously I hoped for this to never happen, but the way I work and just how I am, I'm going to get back as soon as possible."
Either way, it seems the D-backs will be without one of their better starting pitchers for a while.
The team is exploring a number of options to replace Miller, including Archie Bradley, who lost out in a bid for the rotation this spring, but he pitched well enough to win a spot in the bullpen. Bradley has a 0.79 ERA in 11 1/3 innings this year.
Another option would be to call up a starter from Triple-A Reno. For at least the next couple of days, reliever Silvino Bracho was promoted from Reno to give some depth in the bullpen.
"Extremely unfortunate for Shelby and for this organization," D-backs manager Torey Lovullo said. "He's worked so hard to get back on his feet again. He was throwing the ball very, very well. In the meantime, it means somebody is going to have to step up. Somebody is going to have to take that spot in the rotation, and who that is right now at this point, we still do not know. We're still walking through several options."
Bradley said he felt confident he could step into the rotation, but he emphasized that he had not been told anything and that his main concern right now was for the health of his teammate.