I can see what Fangio is doing with the safety position if it really is going to mimic practice...
Preseason game 1, Dahl starts against the opponents first team offense which lasts about 1 drive. The broncos will not leave Manning in there for long.
Preseason game 2, Spillman gets the start and the coaches get about a quarter of film on him going against the opponents 1st team offense.
Preseason game 3, Reid gets the start in the most realistic game of preseason... this will give the coaches the best impression of whether he is ready to start or not as he could get up to a half against the opponents 1st team offense.
Preseason game 4, No one curr...
Now obviously he may rotate safeties within the period the 1st team offense is in there, but it seems to me that they have set up the competition so that Reid will have an extended opportunity to prove himself and to a lesser extent Spillman. Here's hoping Reid impresses