One of the things former Minnesota Vikings safety Andrew Sendejo is most remembered for is his outspoken stance regarding physicality in the modern NFL. Over the years the league has imposed increasingly stricter rules to ensure player safety, but that came at a cost. Because of these new rules, NFL defenders are put in a precarious situation where they're constantly trying to avoid being penalized and a byproduct of that is defenders playing scared.
Andrew Sendejo possibly sending a message to the NFL with his hat. Said he has been wearing for a while but that it still applies.