Strong Safety vs. Free Safety
There are two "safety" positions on the defense in the game of football. Sometimes their jobs overlap, but many times they are assigned very distinct roles in the defense.
Strong Safety
The strong safety is more tuned in to the running game on the whole. He's a linebacker with the speed of a safety. He has to cover receivers, but has to be a strong force on a running play.
Free Safety
The free safety is the last line of defense on the football field. He's definitely more of a pass-minded defender. His job is to sit back, survey, and attack where needed. Although with the sophistication of some offenses, he will inevitably be required to "fill" on running plays, as he's often the only one unblocked.
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