Beathard suffered a foot sprain in Saturday's preseason tilt against the Texans and will be evaluated further Monday, ESPN's Nick Wagoner reports.
There were no reports of an injury after Beathard completed 10 of 17 passes for 82 yards in relief of Jimmy Garoppolo, so the foot injury must have flared up after he left the contest. The 49ers will run tests on the backup quarterback's foot Monday, and Nick Mullens figures to move up the depth chart if Beathard is unable to go next week against the Colts.