The coach added he hasn't yet decided whether to place Hightower on injured reserve or to make any other roster adjustments.
The running back went down early in the third quarter of the Redskins' 33-20 loss to Carolina Sunday while trying to cut back after taking a handoff.
He has compiled 321 yards and one touchdown on 84 attempts in five games this year.
Moss, meanwhile, has hauled down 25 passes for 301 yards and two scores in 2011. He left Sunday's game in the first quarter.