the interpretation of both "assists" and "key pass" that are subject to an individuals assessment rather than objective test.
Hypotheticals,
If a player like Walker say, gets put through down the right side completely un-marked and crosses to two unmarked team mates in the penalty box, is it a "key pass" and therefore "a chance created" if
a) he puts it across and empty goal and no-one gets a touch
b) he puts it directly in the path of both attackers, but neither get a touch and therefore no attempt at goal arises
c) he puts it directly into the path of one of the attackers who fails to control it but would otherwise be trying an attempt on goal
d) he puts it into the path of one of the attackers but he slices it backwards and its not clear whether he was trying for goal or to set up his other team-mate
e) he puts it behind both attackers who therefore fail to connect with what most would consider a clear-cut chance?
and finally , if the pass to Walker was a magnificent 50 yard defence splitting pass (which cut open the defence in the first place) to leave him with this golden opportunity, under the current definition, this would not be considered a "key pass", while I would suggest most people would think it was.