I think the staff as a whole lacked experience and they sought coaches with more experience. Marrone was one of them. 

 

Any GM is aware of potential interim coaches that lie in wait on his staff should a HC change be necessary. That's their job. 

Did Caldwell hire Marrone with this in mind?  Doubtful.  

He just had a chance to get a great line coach for a line sorely in need of help and he jumped on it.

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