I was there at Oxford, he didn't get injured due to be knackered or whatever, he went through the back of an Oxford player on the halfway line clearing the ball and got tangled up doing so. Could've happened to the fittest player on the block.
Said as much myself, ffs he's only played 5 times for us, and I think twice for Bristol City b4 joing us. It's an impact injury and like you say could just as easily happen in training.