IMO, Warner isn't so much 'washed up' as he is reverted to normal status ... I thought at the time they were winning big in StL that he was playing over his head and have seen nothing in the interim to make me think differently ...
It's sorta like the fresman coach I had in HS ... he kept trying to make a receiver out of me, because he saw me make a sensational catch ... problem is, it was the ONLY sensational catch I ever made in my life ... after that single catch, I reverted to form and future coaches were smart enough to play me in positions that didn't require me to touch the ball ...
Similarly, I think Warner had a brief, albeit somewhat spectacular period of greatness, then quickly reverted to form ...