Week 3 of the NFL season kicks off Thursday night, yet the league's trademark parity is already hugely evident with 20 of its 32 teams sitting at .500.

In a year that marks their 40th anniversary, it seems the 17-0 Miami Dolphins from 1972 need not worry another team will move into their vaunted neighborhood this season.

But six are still mathematically alive for a shot at 19-0, though that number will be reduced to at least four by Monday: