Here is the presentation on how to analytically determine how "clutch" a player is:
http://rinkstats.com/2015/02/sloan-presentation-slides/
To summarize, the author has determined that the average NHL goal increases the chance a team will win by 17%.
He then determined how much a player's goals affected the outcome for the team.
As noted Glencross was well below the average.
Also the Player A and Player B in his presentation are actual players. Spoiler for who they are: