Quick, name the last time the Michigan State football program lost a player the caliber of Ed Davis to a season-ending injury.
I'll save you some time – don't even look at the 2013 or 2014 season. Those teams, which combined to go 24-3, bring home Rose and Cotton trophies and score consecutive top-5 finishes, were virtually free of major, long-term injuries.
Those teams earned what they got. But health luck is always part of the story. The 2013 and 2014 MSU teams had it ("star" LB Mylan Hicks missing most of last season was the biggest loss, while "star" LB Jairus Jones' season-ending injury in the fourth game was the biggie of 2013).