The Carolina Panthers conducted a walkthrough Wednesday due to the short week, and Young did not participate due to the ankle issue.
Coach Frank Reich told reporters it wasn't clear when Young suffered the injury, and he doesn't yet know the QB's status for Sunday in Seattle. The club will have a better idea on Thursday.
Young's best drive Monday came on the final possession, where he generated 61 of his 153 passing yards and a touchdown.
It's been a rough go for Young through two weeks, as the Panthers have struggled to protect the young signal-caller and the wide receivers have offered little room for error. In two losses, Young has completed 59.2 percent of 71 attempts for 299 yards, two TDs and two interceptions.
If Young can't play Sunday, backup Andy Dalton would make the start. Reich noted Wednesday that there wouldn't be much of a difference between game plans for Dalton and Young. The Panthers also added quarterback Jake Luton to the practice squad on Wednesday.