I think to me the concern is the way the Cards have played the last few years, CB's are often on an island and if you get faked out badly or just blow a coverage it's going to be a big gain or a TD. That's the problem I had with Bethel too, too many misses where his guy is going to get a huge gain because there's no help.
Against the Raiders Williams got beaten badly 3 times early in the game, any one of which could have been a big play or a TD if a better throw had been made. He got beat a couple of times badly in the SD game. Now you put that in a regular season game with him going up against good NFL Wr's on every down for 4 quarters and it seems obvious if he plays now like he's played the first 2 games, he's going to get picked on mercilessly and give up some huge plays.
I think he clearly has talent and in time maybe he becomes a really good CB, the concern is him starting now on a team that has a chance to go a long ways. We really need Bethel to get back and play better than he did last year.