He may have passed the concussion protocol, and been cleared to play, but he was obviously still dealing with a concussion. A good coach would have recognized it and pulled him. A great coach would have recognized it before the game started.
To follow up on this. Roughly 20% of players clear protocol without missing a game, so it isn't unprecedented. I'm not sure how many of them do it on a short week, and only get cleared on the day before kickoff, but it's a small number. Purdy is the first one to clear and play in one week this season.
Purdy did all right, but, to my eye, played slightly off during the first three quarters. It looked like they game planned around it, leaning heavily on the run game, and giving him easy reads and throws, but that is pretty much their base offensive formula, so it may not have been an adjustment.
I believe Purdy aggravated his concussion on the Pratt interception, at the end of the 3rd quarter. Niners were down 17-10, and Purdy put up a slightly underthrown pass that was tipped and intercepted. Hell of a play by Pratt, BTW. On the runback, Purdy was blocked, and hit his head on the turf. I think he aggravated the concussion on that hit.
Next play for Purdy resulted in the second interception, on a bad read and throw. 9 times out of 10, Purdy doesn't make that throw. I think he was off.
The subsequent drive put Cincinnati up 24-10. Purdy put together a pretty good drive to get back to 24-17, then the Bengals made it 31-17.
At 1:59 of the 4th quarter, Purdy throws another int, that was negated by a bullshit roughing the passer penalty. However, he clearly aggravated the concussion, and should not have been left in the game.
Why they put him back on the field, and made him actually play, down 31-17, with 12 seconds left, after clearly hitting his head once, and debatably twice, is beyond me.
They simply don't give a shit about his long-term health.
He shouldn't have played this game, and he should have been pulled during the game.