Ridder signed with the Vikings' practice squad Thursday.
The quarterback was with the team earlier in the season when J.J. McCarthy was sidelined with an ankle injury, but he was waived in early October. With McCarthy now working through the concussion protocol and Carson Wentz out for the year with a shoulder injury, Ridder is back. Max Brosmer is taking first-team reps for the Vikings this week, though McCarthy did practice on a limited basis Wednesday.