Johnson (rib) left the game in the fourth quarter of the 49ers' 28-21 win over the Packers on Friday, David Lombardi of The Athletic reports.
An already depleted San Francisco secondary took another blow when Johnson was hurt late in the contest. Emmanuel Moseley (hamstring), Charvarius Ward (groin) and Jason Verrett (knee) also missed the contest, leaving Ambry Thomas and Deommodore Lenoir as the top options at cornerback until the aforementioned four options recover from injury.