DENVER — Tall and imposing, indomitable even, 6-foot-8 with shoulders and a back broad enough to push a pickup truck.

He was a star lineman on a state championship team in high school and for the University of Colorado Buffaloes, where he set a team record for starts and minutes played. He was an Associated Press third-team all-American and played three years in the N.F.L.

Yet the word that jumps most quickly to mind when talking to Ryan Miller is “fragile.”

Hits, concussive and subconcussive, have laid him low. Head bursting, nausea rising, please shut off the lights, please. I interviewed Miller twice, our talks separated by 22 months, and he is doing better, which is not to suggest this thoughtful and soft-spoken 29-year-old is anywhere near what he wants to be.

When I met him in 2017 Miller had spent the previous hour in a darkened room, breathing slowly. He would get into his car and sit for hours, trying to remember where he intended to go. He would walk into airports, and lights and noise and crowds made him want to curl into a fetal ball. Since then he has gotten better with therapy and diet, and he has lost a lot of weight. He’s healthier, and yet. …