He held onto the ball "too long" because Martz kept running long developing plays without any extra blockers, among the many other stupid things he did trying to salve his ego after losing the Super Bowl to the Patriots. He put Warner in a shit position and then threw him under the bus when things went south. He had a slight amount of decency to admit - much, much later, after he was out of coaching - that he got Kurt killed.
The injuries, including the hand injury, probably doesn't happen if Martz does a little introspection and a little bit of adjusting to the changing reality. He didn't, and Kurt took the brunt of it initially, although Rams fans in general took it as the team fell apart.