He's asked about it a lot and I know it's hard for a guy who ran for 2,006 yards in 2009 not to think he can reach two grand again. There are reasons Chris Johnson can fare well again, and Adam Schefter hits them in this video. He doesn't mention the primary reason Johnson's got no chance of getting anywhere near 2,000. His name is Shonn Greene.
I ran through numbers back in March that illustrate just how difficult it would be for CJ to get to the milestone again.