Hockey is a very physical sport, and the fact that he hasn't gotten hurt since 2009 is insanely impressive. It's even more impressive that he's been able to consistently be an NHL caliber player during that time, never getting healthy scratched.
For Kessel personally, that streak is coming to an end. The Vegas Golden Knights are scratching him tonight, according to Elliotte Friedman.
The good news is, the streak actually remains alive! The playoffs don't count towards his streak. Only the regular season counts. So this scratching isn't detrimental to the actual streak. Just the personal streak Kessel had going for him.