The Falcons spurned a 21-point advantage in the International Series game, as the Lions rallied in the second half and secured the win as time expired when Matt Prater kicked a 48-yard field goal through the posts.
Ryan told reporters: "This is probably as tough a loss to take as any I've been a part of, and really feel like we had a lot of different chances to win that ballgame and consistently didn't make plays when we needed to. You know, we've got to get back home.
"We've got to find a way to get better over the course of the bye week, and I think everybody needs to look in the mirror and self critique and really when we get back to work, have a great mindset and a great sense of focus."
The Falcons are 2-6 in their season following their defeat to the Lions.