It's rumored that he had both his knee and his shoulder worked on since the season ended, so the questions that come to mind are 1) when did each injury occur, and 2) how much did it affect running/throwing? I've gone back and rewatched his fumble early in the Colorado game multiple times because I instinctively and instantly worried that he'd reinjured either his shoulder or his knee when he got hit so hard, so low, and landed awkwardly. He got up and used his throwing hand to unsnap his helmet like nothing had happened, but I always thought that maybe something did, and part of why I thought that was because of how strange everything got as the game went on. He played late like he was hurt, and Frost not calling any passing plays in OT would have fit that theory. Frost doesn't discuss injuries, so it made sense that he didn't really have a reasonable answer ready after the game for why his play-calling got so conservative. IF Martinez was injured during the Colorado game, Frost wasn't going to advertise it, and he's not very good at lying, so he'd probably give an awkward answer, much like what he actually did.
It's just a theory.