Defending Trips can be difficult when trying to stay in a split-field look. Some defensive coordinators opt to “kick” the backside safety to the three WR side in order to keep the LBs “capped,” or assisted with verticals by a Safety. Another way to play Trips is to slide the backside Safety into the box. This allows the overhang to the #3 WR to exit the box and take any vertical by #3 (with limited support by the front side safety). Finally, a coach can always spin to Cover 3 versus Trips.
Trips is an odd formation because it puts three speedy players to one side of the defense. It literally “stresses” the defense. If kicking the coverage, the backside CB is exposed to one-on-ones. Spin to single-high and a coach has created one-on-one matchups across the board. In order to stay in a split-field look and support the backside CB, a coach needs to stretch the coverage. If based out of Quarters, a way to do this is to run Stress Coverage to the Trips side.
What Stress does is take the basic Quarters coverage (I refer to it as SKY), and stretches it across the Trips formation. This leaves the defense in a true split-field look. The front side is independent of the back side, and vice versa. By staying in a two-high structure, the defense can manipulate the coverage and fits to the backside in order to fit what the coach needs. In Stress, as stated, the regular Sky coverage is stretched.