Oakland’s running game has fared just fine without Darren McFadden, their regular starting running back who’s officially missed three games, but unofficially it’s four because he only had two carries in a Week 7 loss to Kansas City before leaving in the first quarter with a foot sprain.

Michael Bush was promptly handed the starting role, and he’s been highly effective, just as he’s been in the past during McFadden’s frequent injuries. Even during that Week 7 28-0 blowout he still rushed for 99 yards, and overall during McFadden’s absence he’s had 461 yards rushing yards while adding 150 receiving yards and scoring three times.

Now the Raiders have to hope that Bush can keep taking the pounding for at least a few more weeks, because NFL.com’s Jason La Canfora is reporting that McFadden will likely be out until Week 14 at the earliest. The short-term outlook for McFadden’s injury doesn’t sound promising.

McFadden still is very limited and unable to do much. The source said playing this week is not feasible for McFadden, and in all likelihood, next week’s game is not probable for his return, either.

While Bush’s play has allowed the Raiders to be patient with McFadden, there has to be at least mild concern about his ability to withstand the continued physical punishment that comes with the starting role. He’s been given 30 carries in each of the last two weeks, and he’s averaged 24 carries per game since McFadden went down.

Bush has either been a backup or part of a backfield platoon throughout his four-year career, and his highest per game carry average was the 11.3 he received last year. In 2010 Bush also set his career-high in total carries with 158, and through only 10 games this year he already has 139, setting a pace to easily eclipse that high.

Any concern about Bush’s workload is heightened by the widespread injuries to Oakland’s receivers, a training room bug that places an even greater emphasis on the Raiders’ running game. Jacoby Ford will likely miss his second straight game this week, while the statuses of Darrius Heyward-Bey and Denarius Moore are also uncertain.