The Vikings might be counting on second-year CB Chris Cook more than people realize. If Cook can't make the jump in Year Two, the Vikings could find themselves fairly thin at one of the crucial defensive positions. Cook struggled as a rookie and was felled by two knee injuries that eventually ended his season, but he also flashed playmaker potential. However, in the preseason opener, he also was burned on a long touchdown and crumpled in trying to defend a few run plays. For a player with his size, Cook must be more physical — this Tampa-2-heavy scheme demands it. LCB Antoine Winfield is a rock on one side, and RCB Cedric Griffin is expected back healthy on the other. But Winfield is getting up there in age, and Griffin is a knee injury away from a career-ender. So Cook must be ready to play and play a lot in the nickel — and possibly as an injury-replacement starter. Based on early results, he has some work to do, and there is little established depth behind him.