"I wouldn't say it was affecting me a ton, that's kind of an excuse," said Miller, who went on the DL on Friday, retroactive to Wednesday. "It's just getting back to 100 percent and getting a good feel for the ball and just giving it some rest."
Although Miller said the injury isn't causing physical pain, the DL stint may be coming at a good time. He is 1-6 with a 7.09 ERA in 10 outings, with just one quality start.
Miller has completed six innings just twice. He has walked multiple batters in every start except his first, and has lost five of his last six outings.
"It's definitely a good time to take a break and work on some things," Miller said. "I know I'm a better pitcher than what I've been doing. In my head, I know what I'm capable of and what I'm going to get back to, and there's no doubt about that."
In his first three seasons in the Majors with the Cardinals, Miller was 26-18 with a 3.33 ERA. Last year with the Braves, he posted a career-best 3.02 ERA in a National League-high 33 starts.
"I can't tell you it's going to happen over a week, but I'm going to work as hard as I can to figure it out and get back to where I need to be," Miller said. "I don't think it's too far off, I think it's just going to be a little fix. We have ideas of what we need to do going forward.to straighten things out."
The D-backs could certainly use it. They're a season-worst eight games below .500 at 21-29 and the starting rotation has been an issue. Entering Friday, no D-backs starter had an ERA below 4.15, and their starters combined for a 4.96 ERA.
Jake Rill is a reporter for MLB.com based in Phoenix. This story was not subject to the approval of Major League Baseball or its clubs.