McFadden picked up a strained hamstring during his side's 24-14 loss at the hands of the Washington Redskins, the latest in a long line of injuries for the 26-year-old.
Allen did reveal that he was not expecting McFadden to be sidelined for too long this time around, but stressed the importance of waiting until the injury was fully healed before bringing him back.
"I wouldn't get into characterizing whether it's minor, major. 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," Allen told reporters.
"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."
McFadden has never managed to play more than 13 games in an NFL season and missed almost half of the Raiders' previous 32 matches coming into this season.