Star Wars Rogue One: 37 Easter Eggs & References You Must See
15. Saw Gerrera Foreshadows Darth Vader
One of the defining characteristics of Saw Gerrera in the movie is that he is dressed in a suit of armour which includes special breathing apparatus, which he occasionally takes a huff from, apparently due to injuries sustained during his years of battle.
It's hard not to see this visual and immediately be reminded of Darth Vader, in what's surely a deliberate act of foreshadowing for his brief scenes later on in the movie.