I may be alone, but depending on the circumstances, I would view a poor combine performance as a positive.
A poor showing could mean that the player does not work hard enough to keep himself in a comparable physical condition as his peers. On the other hand, it could be the case that the player is simply physical immature. If the player is physically immature and you believe he will be able to add the muscle later on, you're left with a guy who is likely performing at a high level on the ice despite being physically outmatched by his peers. If he catches up physically, look out.
Sometimes kid's don't have the physique to fill out or develop muscle mass. It happens and is one of the reason's why EDM sucks so much. Their entire top 6 was physically underdeveloped for the last 3 seasons. It leads to poor possession numbers if a team can battle along the boards and come out with the puck.
It's the biggest reason why a kid like Drouin got sent back, or why Ryan Johansson finally lived up to his draft status. Once they are man strong, the pro game is very different, same with Kyle Turris.
Notable top 10 busts or ineffective players due to a lack of physical maturity include Burmistrov, Zach Hammil, Thomas Hickey, Filatov, Peter Mueller, Gilbert Brule, Brian Lee and more.