I hope you intended that "when" to be a temporal conditional, i.e. meaning "if" rather than belief that JT will get hurt, and it's just a matter of time.
It's a matter of when, not if. Every QB gets dinged up from time to time. True for Tebow, Nesbitt, Joe Hamilton, Ben Rothlesbergur, etc. Luck will determine the severity of injuries for the most part. Here's to hoping JT doesn't miss a single snap though.