McFadden's absence would be a blow to Oakland's sputtering offense. The former first-round draft pick is tied for third in the NFL with 392 rushing yards, 35 more than he had all last year. It's the best start by a Raiders running back since Lamont Jordan ran for 424 yards after four games in 2007.
Instead, Oakland will lean heavily on Bush, who has just 10 carries this season after leading the team in rushing in 2009.
Bush's power running is in stark contrast to the quicker, slashing style of McFadden, although Cable doesn't believe the Raiders will alter their offense much because of the change.
"If you look at when Mike's played, it's been the same things," Cable said. "He runs more physical in the box, maybe. You may not get as much play on the perimeter, but you'll get it running downhill at the defense. (McFadden) has been very productive, so we've got to find a way to get that same production, but I think Michael's ready to take that load."
Neither Bush nor McFadden were made available to the media Thursday. McFadden didn't attend practice.
McFadden isn't the only Oakland player hurting.
Backup running back Michael Bennett (hamstring), left tackle Robert Gallery (hamstring), defensive tackle John Henderson (foot) and linebacker Thomas Howard ((knee) sat out Wednesday's workout. Linebacker Quentin Groves (hamstring) was limited in practice but isn't expected to play much, if at all, against San Diego.
Rock Cartwright has taken only a handful of plays on offense for Oakland this season and will be Bush's backup if McFadden and Bennett are ruled out of the game.
The Raiders could receive a lift if Gallery is cleared to play. Gallery hasn't played in three weeks, but Cable apparently is willing to start the lineman if he practices Friday.
"The workout was good this morning, so if we can get some work out of him tomorrow, we'll see what happens," Cable said. "It depends on how the work goes. If it looks erratic and all that, it's not worth doing that."
Copyright 2010 by The Associated Press