While the fullback position isn't as glamorous or important as other positions, the good fullbacks may wind up being difference makers in the outcomes of the upcoming Divisional Round matchups.
With the way the NFL has shifted to a pass-first league, the demand for throwback-style physical fullbacks has declined greatly. That isn't to say there aren't a few classic fullbacks remaining in the league, though.
Ranking fullbacks can be difficult because a lot of what they do doesn't translate to the stat sheet. Also, more than most positions, the play style of the team directly affects what the fullback is tasked to do, which in some cases is primarily blocking.
An argument could be made that fullbacks are on the verge of extinction, but fullbacks still play vital roles for certain teams, including quite a few teams still in the playoffs.