Any pursuit of an athletically demanding nature is going to see diminishing returns as one ages. It might be delayed longer for some than others, but if you work in a profession where your job is to compete against the best athletes in the world who could be considerably younger than you, there is no forgiveness against a reduction in athletic ability over time.
Future Hall of Fame cornerback Patrick Peterson is well aware of that, and understands that this next, likely last chapter of his professional career with the Pittsburgh Steelers will call for change. The team has told him as much.