ALLEN PARK -- Yet another Detroit Lions player was allowed to finish a game with a brain injury.

This time it was Don Barclay, who played all 64 offensive snaps in Sunday's 26-17 loss against Cincinnati. Two days later, he was placed on injured reserve with a concussion.

He is the third Lions offensive lineman this season to finish a game with a brain injury, following T.J. Lang (who missed one game) and center Travis Swanson (who has missed two games and counting).

Swanson also finished a game last year with a concussion, before missing the final five weeks of the season. Throw in cornerback Rashean Mathis and tight end Dorin Dickerson, and six Lions players are known to have finished games with brain injuries under coach Jim Caldwell.

Caldwell said earlier this season he still believes the concussion protocol is working.

"I do think that the protocol we have in place takes the players' health and safety first and foremost," Caldwell said. "When there is something that comes up, it's addressed immediately. They're evaluated immediately, and then a determination is made immediately by guys who have spent their lifetime in that particular field."

If the protocol is working, perhaps it is players who aren't doing a good enough job reporting symptoms?

"It's hard for me to assess, but we've had a couple issues with symptoms showing up after the game, and the player comes in and talks to doctors," Caldwell said. "So I do think if they're feeling something, they'll let them know."

Caldwell said the club doesn't need to talk to players more about the importance of self-reporting brain injuries, because they do it before every season.

"That goes without saying these days, in terms of the importance of it and those kinds of things," he said. "And our players are well aware of all we go through. They go through a complete and thorough introduction before the pads are put on, and it's run by our doctors, our medical personnel."

The Lions filled Barclay's roster spot by promoting Hakeem Valles from the practice squad. Valles is a player the club is so intrigued by, that it has paid him more than than practice squad minimum to keep him in Detroit.