Part of being successful in the playoffs and sustaining a good level of play is staying healthy.
Similar to Demko, Petey has to be smart about how hard he is training and playing in the early part of the season and do his best to stay healthy going into the post-season. This is also on the medical staff.
It is possible that he is just a naturally frail person. Seeing how often he just randomly falls over like Bambi, its possible he is just a frail dude that is prone to wearing down on a season by season basis. Weak knees, etc.
100 point regular seasons are great. And they help to push the team into a playoff spot, but they don't count for much if he is hurt and ineffective in close playoff series.