No playing on average 17 games a season attributes to being injury prone.
Shame I was talking about this one incident.
Being injury prone is about more than having some kind of congenital weakness of muscle or ligaments. It's also about being reckless and/or having a poor technique when going into a challenge (which will include challenging for headers, before you say anything). Phil Jones being a classic example. So yes, a fractured cheek-bone could be part of the bigger picture of a player being injury prone.
While I can understand your argument and agree with it. This was an accident. If he broke he cheek in a car accident would it come down to him being injury prone? If the exact same contact was made with De Gea and he broke his cheek, would we label him as potentially injury prone?
Again, I understand the argument but far too often United fans need a reason for something. Take a bad performance for example, we read so much into it, players ability, the system, the manager, the players effort, everything we can think of we use as a reason to pick a players performance apart but we miss the most basic things that have the biggest impacts, did he have a shit breakfast? Did he get a good sleep? Was his baby keeping him up all night? Is he having a tough time with his wife? etc
So now with complete accidents, some try to reason it. Everyone would be far better off just accepting shit happens.