I think the reason people sometimes view Fox as a liability is:
1. Getting burned against Illinois in '02- every great CB has that type of game where a guy torches him, and the big Illini wr's did exactly that. Luckily, we won.
2. He gives up a lot of the 5-10 yard short passes b/c he plays soft coverage. Now whether that is b/c of the defensive system OSU is playing or that he just plays soft man is up for debate. However, it is true that he rarely if ever gives up the long bomb.
3. He's white- yes it might not be a conscious judgment but the stigma is there as much as you may want to be politically correct and pretend its not. Some people, even if they might not consciously realize it, seem to assert a lower "athleticism" value to a white athlete playing a position like CB. Not saying everyone, but you'd be naive to think it doesnt play some part in some people's opinions, perhaps not overty but subconsciously.
4. He is still perceived by some as a safety filling in at CB.
With that said, I think we need a steady CB like Fox b/c that's a position where consistency is of the highest importance. A guy like Underwood might be more talented, but the rap on EJ is that he takes too many chances. Same with Gamble- got burned against Wisky, and his major weakness was biting on double moves. Fox, on the other hand, is a very smart player who is willing to give up the short pass to make sure we dont give up a back breaking long bomb, which is perfect for our defensive philosophy. Remember, we no longer play the old Pugac blitz em to death with corners in constant iso situations w/ Springs, Winfield, Plummer...Then you have crap like the "springs slips" happen and it really does break your back. Anyways, bottom line is having a senior CB with bigtime experience and talent like Fox is a big advantage for us.