Sending a rookie up against a Rex Ryan defense is a very tough task. Josh Freeman went 14 for 33 with 93 yards and 3 interceptions last year. Being a rookie quarterback in the NFL is incredibly difficult. These players must adjust to the speed of the game, mastering a new playbook, and getting comfortable with teammates. Ryan shows exotic fronts that perplex veterans.
McCoy is at a distinct disadvantage. No team in the Big XII plays defense like this. The conference is dominated by pass happy spread offenses. Defenses adjust to this by playing vanilla zone based schemes. Most of the time, quarterbacks have to face subpackages of conventional defenses. They don't have to read man coverage much.
McCoy has started three games. Two of these opponents run zone based defenses, Pittsburgh and New England. The quarterback played pretty well. The one time he had to play a man based opponent that attacks, New Orleans, he threw for only 74 yards. The quarterback and the coaching staff minimized the chances for mistakes since the Browns led for most of the game, but it's tough to imagine McCoy has much of a comfort level against man coverage, particularly corners with the ball skills of Antonio Cromartie and Darrelle Revis.
One attribute McCoy has which gives me concern is mobility. He can extend plays and make runs with his feet. The Jets have too many instances where guys fly up field on blitzes, overrun the quarterback, and leave room to scramble for big gains. He had a 175 yard rushing game at Texas A&M last year. While I don't think the Browns will want to expose him to hits on too many designed runs, he is capable of making things happen on broken plays.