It's almost like the NFL is a tough league or something. Good teams get beat by lesser teams every week -- and I'm not sure the Panthers are that much worse than the Lions. Going 9-1 to close the season was always an improbable feat, regardless of who they had to play.
It would be even better for the young Lions players who have never been to the playoffs before. The experience of actual win-or-go-home playoff intensity now would be invaluable for them, and put the rebuild way ahead of schedule.