The Oakland Raiders are not only facing the idea that Terrelle Pryor might not play on Sunday, but now they have to handle an investigation by the NFL Players Association. The quarterback suffered a concussion late in the game during Monday night's loss to the Denver Broncos and the Raiders are facing questions about how they handled the injury.

Pryor suffered a helmet-to-helmet hit from linebacker Wesley Woodyard late in the fourth quarter. Pryor played two more snaps before officially being taken back to the locker room by the medical staff. Sources report to ESPN that the move was considered questionable and the NFLPA is now getting involved.

Per NFL rules, Pryor was not allowed to speak to the media after the game, but beat writers reported he looked fine standing by his locker after the loss. Head coach Dennis Allen said after the game that Pryor should no signs of suffering a concussion after the initial hit. He believed the team followed all rules accordingly. Game tap shows Pryor possibly went to the sidelines to speak with Allen before returning for action on the field. That is what the NFLPA is currently investigating.

Pryor took to Twitter to apologize for the loss and indicated his memory was shaken. The Raiders quarterback tweeted, "Sorry about the loss RaiderNation. I don't remember much! Good hit by whoever it was. I heard out team fought well...We will be back!" Pryor followed that up with a tweet saying he was fine and will be back in action soon. The quarterback will have to undergo a series of tests before being cleared for play again.

This means that Pryor's status for Sunday is officially questionable and veteran Matt Flynn could see his first start of the season. The current backup says he is prepared to play whenever his name is called. He took over on Monday night with just over six minutes to play. His 19-yard pass set up a touchdown to ease the blow.

"You've got to be ready at any time," Flynn said, via the San Mercury News. "Obviously the game didn't go the way we wanted to. But I got in there, we had good field position and I was able to get it in, so we were fortunate in that aspect."

Pryor won the starting job just before the season began and has handled the role well. He finished Monday's game going 19 for 28 in passing for 281 yards and 73-yard touchdown pass. For the second-straight game he did not commit a turnover while rushing for another 36 yards on four carries. Safety Charles Woodson remains hopeful that Pryor will continue his upward momentum and be healthy for Sunday.