NFL players get hurt. They get suspended. They get old. They lose their talent. They leave in free agency, and sometimes they get traded. Defenses move from a 4-3 to a 3-4 (and vice versa), and talented players no longer fit the new scheme. And on rare occasions, they'd rather be firefighters, they do sit-ups in their driveway, or they throw up gang signs and get cut (I kid!).
The long-term viability of players in the NFL are often complete unknowns. However, one thing is a certainty -- NFL rosters turn over very rapidly.
Only 33.5% of NFL players who started their team's last game in 2011 started that same team's last game in 2013. That is incredibly low roster stability. The following is a chart of how many players on each team started their team's final game both in 2011 and 2013:
As you can see, only 2 teams in the NFL, the 49ers and Redskins, had at least 11 players (or half their starters) start their final games in both 2011 and 2013. The Giants won the Super Bowl after the 2011 season and only had 6 starters from that game (27%) start their finale in 2013.
When we think of players entering the NFL, we think of them reaching their prime after being in the league for about 3 years. By the time those players reach their prime, there's an outstanding chance the roster around them will have changed dramatically. Look at the Broncos, for example. They reached the Super Bowl this past season, and only 4 starters in that game started for the 2011 playoff team that featured Tim Tebow.
Some of that roster instability is predictive. For example, it was predictive that Michael Vick would miss a few games every year due to injury. Going forward, it's predictive that Todd Herremans may not be starting in the NFL in 2016 because of his age and mileage. But there is certainly plenty of unpredictability, such as injuries, unforeseen player decline, bad scheme fits, and other unknown scenarios to go around as well.
This time of year, you'll often hear, "We need to draft an OLB in the 1st round, a safety in the 2nd, a WR in the 3rd, and a CB in the 4th." To begin, whatever players you draft may not be ready to start Week 1 of their rookie seasons, and if you're depending on a rookie to be a major factor in getting you to the Super Bowl, you probably don't have have much of a chance of getting there in the first place. But more importantly, by the time young players are in the NFL for 3 years and ideally they've developed into good starters, the roster is often going to look nothing like the way it did when those players were drafted, and you may have passed on a better player who plays a position that is a need in 2016, but wasn't in 2014.
All offseason fans have heard the "best player available" mantra from the front office. Long term roster instability is a major reason why you should almost never forego a more talented player to draft a position of current need.
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