ALAMEDA, Calif. -- An MRI of fullback Marcel Reece's injured knee came back negative, running back Darren McFadden's strained hamstring remains a question mark and quarterback Terrelle Pryor has to be completely non-symptomatic from his concussion to play this weekend against San Diego.

And that's just taking into account the Raiders' starting offensive backfield a day after Oakland's gut-punch 24-14 loss to Washington.

Center Stefen Wisniewski also has a knee sprain and rookie defensive tackle Stacy McGee has a shoulder issue.

Fullback Marcel Reece, left, and running back Darren McFadden were both knocked out of the Raiders' loss on Sunday and it's still unknown whether either will play this week. Kelley L Cox/USA TODAY Sports

But most eyes are on the legs and head of the Raiders' most explosive playmakers.

"It's really a matter of when's he going to be physically able to go," Raiders coach Dennis Allen said of Reece. "It's not a surgical procedure or anything like that that needs to be done. It's just, whenever he's ready to go."

As for the oft-injured McFadden, who has never played more than 13 games in a season and had missed 13 of Oakland's previous 32 games coming into this season, Allen would not go into detail regarding his latest injury, purportedly suffered on his first carry of the game.

"I wouldn't get into characterizing whether it's minor, major," Allen said. "He's got a hamstring [strain]. I don't expect him to be out a long time but we'll see how he responds. I mean, it's one day after a game."

Then, might McFadden play Sunday against the Chargers?

"Again, we're one day out, so I really don't know.

"We want to make sure that he's healthy. I think hamstring injuries and brain injuries are two totally different things but yeah, we want to make sure that Darren's healthy. We don't want this to be anything that's going to linger."