As any NFL season progresses, circumstances change, as do lineups. Teams must adjust to things like injuries and differences in levels of performance.
For coaches, the approach should always be the same no matter what happens: Put the best players on the field to place the squad in a position to succeed.
It really is that simple.
A fine line exists between a player deserving and needing more time on the field. In either case, having those individuals in the lineup to see what they can provide through expanded roles serves the best interests of the team.