No question Brad Jones is at the top of the long list, along with Hayward, McMillian, James Jones, Eric Walden, Randall Cobb, EDS, TJ Lang, Des Moses, MD Jennings and Alex Green. They've all stepped up and contributed well in place of starters. Hey, even Mike Neal makes the list. He played well after Raji was first injured, and has continued to do so.
If I had to pick just one, it would be a very difficult call between Brad Jones and Casey Hayward.