The Falcons have come into 2015 with an attitude to get better at every single aspect of their game. After playing poorly enough to have Mike Smith fired despite being the winningest coach in team history, Atlanta needs to really turn it around under Dan Quinn—Smith's replacement.
Quinn is breathing an air of competition into the Falcons in 2015. Very few jobs seem like they are safely with the incumbents on the team. Of those, there are quite a few players who started in 2014 who could very well be out of jobs in 2015.
They come from all over the team, and it's very likely that at least half of them are cut at the end of training camp.