IOWA CITY, Iowa (AP) – Iowa coach Kirk Ferentz says quarterback A.J. Derby will likely open the season as the backup to junior James Vandenberg.  Derby, a 6-foot-4, 232-pound redshirt freshman from Iowa City, would get the nod over James Wienke as the reserve behind Vandenberg. Ferentz on Tuesday praised Derby for his size, quick feet and competitiveness. But it appears unlikely that the Hawkeyes will prepare special packages for Derby simply to get him on the field.  Derby could see playing time as early as Saturday, though, when the Hawkeyes host FCS school Tennessee Tech.  Iowa has won its last 10 openers by an average of 31.5 points, allowing backups like Derby to get experience.