The Cowboys could draft North Carolina offensive guard Jonathan Cooper. Or maybe Alabama offensive guard Chance Warmack. Or it could be Texas safety Kenny Vaccaro or North Carolina defensive tackle Sylvester Williams. Everyone has his opinion on whom the Cowboys will select with the 18th pick. ESPN draft analyst Mel Kiper Jr. is betting on a defensive player, possibly Vaccaro or Williams, with the Cowboys switching from the 3-4 to the 4-3.