We had a lot of trouble with the instability of the site last night. Sadly, it is caused by the still running offseason processing which we just need to wait out.
Since the start of season 30 or even a bit sooner, changes in the game engine changed the way "Let Coach Decide" works. Until then, the starting lineup has been respected, at least at match beginning. Afterwards, it wasn't, the coach truly picks his own lineups, starters and all. We are not sure if this is something we even intend to fix. That's why your player was in the starting lineup. I suggest using "Strictly follow depth chart" in the future.
As for the injury, you have a doctor with the "Taping Injuries" specialty, and that's what he did.