Head coach Jim Harbaugh told reporters that Mickens (shoulder) won't practice Wednesday and "could miss time," Kris Rhim of ESPN.com reports.
The rookie safety from Clemson exited the Week 15 win over the Chiefs with a shoulder injury, and it appears that issue could sideline him further. Mickens' practice participation Thursday and Friday will likely provide the best indication of whether he can suit up for Sunday's matchup against the Cowboys.