In this photograph taken on Thursday, Aug. 16, 2012, Denver Broncos veteran wide receiver Andre Caldwell looks over the team's playbook on a team-issued computer tablet as he walks off the training field at Broncos' headquarters in Englewood, Colo. Players like the convenience of storing the playbook on computer tablets, which has prompted six NFL teams to retire the traditional printed book in favor of the computer screen. (AP Photo/David Zalubowski)