FORT WORTH, Tex. -- News travels fast in the NFL and when one head coach makes a bold, stunning, some may say crazy decision to promote his offensive line coach to defensive coordinator, it ricochets to the game's biggest stage.

In case you woke up thinking that Andy Reid's decision to name Juan Castillo as his new defensive coordinator was a bad dream, it was not. It was as real as the assessment Steelers offensive coordinator Bruce Arians made about the potential fallout from such a decision.

"Andy's job is probably on the line," Arians said Thursday. "But I know this -- he replaced [Castillo] with a good offensive line. Howard Mudd is the absolute best. The quality of the staff is there. Now it's just a matter of game day and how they're going to handle it."

Arians has to gotten know Castillo through coaching channels and is familiar with his legendary work ethic.

"Nobody's going to work harder because Juan is one of the hardest-working coaches that I know," Arians said. "When you block as many things as Juan has blocked you kind of know what's sound on defense and what's not."

Still, there are very legitimate questions about how Castillo will handle some of the chores of the job he is not accustomed to.

"Now matching wits with an offensive coordinator -- the scheme's going to be sound. He knows what's sound," Arians said. "It's having the gut calls, when to blitz, when not to blitz, when to play this, when to play that. That would be the only question I would have."

Steelers linebackers coach Keith Butler was rumored to be one of the candidates for the opening.

"I think Andy's sitting there thinking, 'How can I beat protections?'" Butler said. "And he's got a guy that's trying to figure out how to protect against every team in the league. So this guy has probably seen every blitz known to man. So I can see Andy's point of view."

No one seems to recall such a move ever taking place in the NFL.

"No, I haven't," Butler said. "But he's not doing it to get fired I will tell you that."

Steelers offensive line coach Sean Kugler actually played under Reid in Texas El-Paso when Reid was his position coach. Kugler laughed when he was asked if he had any desire to one day be a defensive coordinator.

"I have no aspirations to do that," Kugler said. "If I was asked to do it, I don't know if I would refuse. I enjoy coaching the offensive line. But people are up for different challenges."

Asked for his best Reid story, Kugler obliged.

"Most of them involve food," Kugler said. "The whole time in college all the other coaches used to bring doughnuts and he never brought doughnuts. We used to just kill him on it, 'When are you going to bring the doughnuts?' We used to kid him that he ate them on the way to work."