Right before San Francisco took on the Oakland Raiders Thursday night, one of the women from the squad followed Colin Kaepernick's lead ... and took a knee for "The Star-Spangled Banner."

So far, the woman's identity has not been revealed and neither the team nor the cheerleading squad has commented publicly about it.

Guessing that'll change very shortly.

Of course, the kneeling demonstration BEGAN in San Francisco with Kaepernick. Soon, some of his 49ers teammates (like Eric Reid) joined him. It later spread throughout the league.

Now, Colin is out of the league -- and he believes he's being blackballed because of the protest.

The league had threatened to punish players who didn't stand for the anthem -- but later did away with plans to enforce that policy.