On Saturday, FanRag's Tommy Stokke reported the pitcher will undergo Tommy John surgery to repair the issue.
"It sucks," Miller said Thursday, per Magruder.
According to Magruder, Miller will talk to Dr. James Andrews about the injury. Andrews was the last of three doctors to read Miller's MRIs, but the pitcher said they all had a similar diagnosis.
This comes after Scott Bordow of AZCentral Sports reported Miller left Sunday's game with right forearm stiffness and was scheduled to have an MRI on Monday.
Miller was a 2015 All-Star for Atlanta Braves with a 3.02 ERA and 1.25 WHIP. However, he pitched a career-high 205.1 innings that season and underwent a drastic falloff in 2016 in his first year with the Diamondbacks.
He notched a 6.15 ERA in 20 starts and 101 innings and was nowhere near the dominant force he was earlier in his career for the Braves and St. Louis Cardinals.
In wake of the injury news, Zachary D. Rymer of Bleacher Report noted "Shelby Miller's velo has been up since spring training. Can't help but wonder if he was overdoing it trying to bounce back from 2015."
The Diamondbacks will now have to rely on their other starters to carry more of the load, including Zack Greinke, Patrick Corbin and Taijuan Walker.