in that situation, every stinkin' time. On offense you NEVER call a time out in that situation. Here is a direct quote from the ESPN article about the game and injury..

His injury occurred on a 4-yard run — even though coaches were trying to get him to take a knee with about a minute to play and Utah State down to one timeout.

Mendenhall said Hill received a sign from the sideline that indicated the clock was going and to run the play but looked away as the "victory" signal came in momentarily thereafter.

That meant Hill should have taken a knee on the season-ending play, as he did the next two plays.

The coaches sent in the signal, and tried to get him to take a knee, but he missed the signal and went with a different play. It's a game, and stuff happens. Doman had a lot to be held accountable for based on his running of the offense, but this play was not his fault.