Arizona Diamondbacks right-hander Shelby Miller has found himself back in Triple-A following a miserable first half, and chief baseball officer Tony La Russa was cryptic about one potential factor the organization believes led to his struggles on the mound.

"There was something that, and I know this is really going to sound kind of yucky and kind of mysterious, but there was an issue that came up - believe me, it was not illegal, it wasn't anything dramatically character-wise that was a problem - but there was something that came into the way that Shelby prepared that worked against him and not for him," La Russa said Friday to Bickley and Marotta on Arizona Sports 98.7 FM.

"We really didn't get onto it and solve it until well into the struggles into the season, and now; it's a health thing that we thought, he thought would be a healthier thing to do, and we realized it wasn't working for him."

La Russa failed to get into specifics about what exactly was inhibiting the 25-year-old, who owns a 7.14 ERA over 14 starts.

"It was more a diet thing," La Russa said. "It wasn't a health - in terms of his arm - or it wasn't anything he was doing that was dangerous. It was just something that became ill-advised as far as his diet."

It's been a difficult week for Miller. He was optioned to the minors Thursday, and general manager Dave Stewart said publicly the following day that trading for the former All-Star has, so far, not worked out.