MINNEAPOLIS, Minnesota, Dec 31, 2010 (AFP) – Brett Favre was listed on Friday by the Minnesota Vikings as doubtful for the team’s matchup Sunday at Detroit, in what was expected to be the final game of Favre’s 20-year career.

The 41-year-old quarterback, who has unretired for the past three years to extend his historic National Football League career, has vowed that this will be his final season.

Favre, the NFL’s all-time passing leader in most major categories, had a 297-game streak of starts snapped earlier this month due to injury and suffered a concussion in a loss to Chicago on December 20, missing last week’s game.

NFL rules require players to pass medical tests before being allowed to play following a concussion. Favre has until Saturday to pass the fitness exams in order to be eligible to play at Detroit.

Vikings interim coach Leslie Frazier would not rule out Favre for Sunday’s game, but Favre did not participate in any pre-game workouts during Minnesota’s practice session on Friday.