This happens all the time, especially with defensemen. A player looks great for a few months, falls off the map never to be heard from again. It happens in all sports, actually. New York Yankees fans should remember Aaron Small, who helped the team make the playoffs in 2005. By 2006, he was designated for assignment. The New Jersey Devils are in a similar position with Steve Santini.
The 23 year old was great last year, until he wasn’t. Then he went in the complete opposite direction. Santini was in consideration for top-line minutes prior to the Devils acquiring Sami Vatanen.