Officially Angerer is listed as 3rd string MLB behind former Nebraska LB Cody Glenn, but Angerer took over the position when Brackett missed the final 7 quarters of preseason action, despite Glenn being healthy. In addition Glenn is currently the only backup LB with both pro experience at OLB and more than 2 weeks on the roster. Further discounting the usefulness of the Colts publicly available depth chart, the player they listed as their starting strong safety all last week was cut the day before the game.
Angerer stood out in preseason with 36 tackles and 2 sacks, but has been limited to special teams duty so far this year, where he's looked pretty good. Indy runs a zone-heavy, light blitzing D that should be familiar to Angerer, but the most notable difference in Cover-2, which Iowa runs, to Tampa-2, Indy's scheme, is the middle linebackers' assignment. Angerer will be tasked with a much deeper and larger area to defend in the passing game while still holding down the middle against the run.
Cover-2 (with the commonly exploited gaps the Tampa-2 is meant to correct)