The undefeated and seemingly unstoppable defending champions from Green Bay sweep down into Detroit, where a determined bunch of Lions await.

That describes Thursday’s game at Ford Field, where the 10-0 Packers will tangle with the 7-3 Lions. But that was also the situation 49 years ago, the last time an undefeated N.F.L. team played on Thanksgiving. That was when the Packers — 10-0 and the winners of 12 straight games, including the 1961 N.F.L. championship — went to Detroit on Thanksgiving and fell in one of the more stunning losses of the Vince Lombardi era.

The Packers were a fearsome machine in 1962, featuring stars like Bart Starr, Jim Taylor, Paul Hornung, Forrest Gregg, Jerry Kramer, Ray Nitschke and Willie Wood. Through 10 games, they had outscored opponents, 309-74, winning by an average of nearly 24 points. “They had it all,” said Keith Dunnavant, the author “America’s Quarterback,” a recent biography of Starr. “Just about everybody on the team was at their peak.”

Yet the Lions were nearly their equal, especially on defense, where they had five future Hall of Famers, including middle linebacker Joe Schmidt and defensive backs Dick Lane, who was nicknamed Night Train, and Dick LeBeau.