Many teams shy away from running QBs even when they are young. On the defensive side of the ball, the step up in speed from the college game to the NFL is drastic. Run-first QBs who are collegiate sensations, as Kaepernick was, are living on borrowed time in the pro game. They get hit constantly, under circumstances where a single hit can cause an injury that markedly diminishes the quarterback’s future effectiveness as a runner (if it doesn’t end his career outright). Unlike pocket passers with high accuracy (Tom Brady, Peyton Manning, et al.), running QBs tend to decline dramatically, often in a matter of just a few seasons, as defenses adjust to them, cut off their running lanes, make them play to their weaknesses, and continue to pound them.

That is what happened to Kaepernick. By the time he became a free agent this year, he had already deteriorated. He has not been a productive player since 2013. He has not been a regular starting player for three years, and when he has played — in the most consequential position in the game — the results have been awful. He has had a significant injury. And atop all these performance problems, Kaepernick has had no preseason and no playing time this year, with the league now entering the season’s seventh week. Any team that considered signing him would have to factor in his unfamiliarity with the offensive system the team is running. (Pro football teams run very complex offenses, with multiple reads, keys and shifts that change play-to-play depending on what the defense does, and different signals and verbiage that vary from team-to-team. Even experienced quarterbacks need lots of time to master them.)