"Health-wise, he's fine," D-backs general manager Kevin Towers said. "His pitch count got up there. He was struggling with his command, a lot of deep counts, a lot of walks."
Bradley went into Spring Training with a chance to win a spot in the starting rotation but lost out to Randall Delgado and opened the season with Triple-A Reno.
Bradley missed some time with an elbow issue and when he came back, the team moved him to Mobile, where he went 2-3 with a 4.12 ERA in 12 starts.
"It's kind of been a rollercoaster ride for him," Towers said. "He was really good early and then probably discouraged because he didn't make our ballclub, then had the elbow problem. He came back, started off really good in Double-A right off the bat and then went back down again."
Towers speculated that the early start to Spring Training, with the team opening the regular season March 22 in Sydney, Australia, might have impacted Bradley because he had to alter his usual routine to get ready for the season.
The team elected not to give Bradley a promotion to the big leagues for September in large part because he does not have to be added to the 40-man roster this winter. The D-backs have said Bradley will pitch in the Arizona Fall League for the Salt River Rafters starting in October.
"We certainly haven't lost any confidence in him," Towers said. "I think the tenderness in the elbow, we were worried, but there's no structural damage. I'm sure that's probably been in the back of his mind as the season went along. He's got to get that walk rate down and that fastball command back. Up here, that's paramount. That's probably why we should not bring him up in September. His fastball command is not where it needs to be to have success up here."