McGahee was having success against a Charger's defense that was struggling to stop him early. With seven carries for 55 yards, he was the foil to allow Peyton Manning to work the play-action pass, and find his receivers, not that the Broncos' quarterback is having too much trouble with 63 yards and a touchdown halfway through the second quarter.
If Denver's feature back is unable to return, the load will fall on backup Ronnie Hillman. The third-round rookie has had success in limited time this season, carrying the ball 37 times for 145 yards. With just two carries against San Diego, he's picking up where McGahee left off, rushing twice for 22 yards, including an impressive 21-yard run.
With a history of knee injuries, any time McGahee leaves the field with a problem in that area, it's concerning.