The Seahawks reverted Mannion to the practice squad Monday.
Mannion was elevated by the Seahawks on Saturday, just one day after joining their practice squad after being let go by the Vikings on Nov. 28. He was active for Sunday's 28-16 loss to the 49ers with Geno Smith (groin) ruled out for the game, and the former acted as the backup to Drew Lock. Mannion didn't see the field Sunday, though he could operate as the backup for the Week 15 game against the Eagles if Smith is unable to play.