Jackson underwent an MRI on Monday. The team has not announced results of that follow-up exam.
Jackson, who missed the entire preseason with a Grade 2 separated shoulder, grabbed at his leg after the play and was worked on by trainers for several minutes on the sideline.
With Jackson sidelined, the Redskins lose their best deep-ball target. Second-year receiver Ryan Grant replaced him in three-receiver sets Sunday, but he lacks the deep speed to threaten defenses. Andre Roberts could get a bump up in targets as well. TE Jordan Reed had a 7-63-1 line Sunday and may continue to be a big-time target in the passing game, and it should also help Pierre Garcon attract more targets.