I think you make fair points in regards to some of those examples. I see most of them as setting the standard rather than being downright stubborn.
If he was just as intense and stubborn at Ajax then why did they not have comparable levels of injury?
Is it possible that our squad is just made up of or built around key players that are just totally not up to the level physically or are somewhat injury prone. Casemiro, Varane, Shaw etc.
Unfortunately statistics on injuries aren't easily found, a quick Google search reveals that Ajax had plenty of key players injured at the same time throughout the season and had situations like Martinez and Shaw with repeat injuries. But without data, it's anecdotal and meaningless.
Injury proness doesn't explain season long repeat injuries and the number of injuries we sustain, particularly the amount of muscle injuries to players with relatively low game-time. Muscle injuries are mainly caused by impact, march overload or training intensity. On average you expect 15 muscle injuries per season with good load management. We cutrently have 7 players out with muscle injuries.
Let's also look at the individual players injury proness.
Casemiro is closing in on being more injured this season than the past 4 seasons combined. He's spent more time out of action with us this season than he was when he fractured his fibula shaft in 2016.
Shaw has been out all season with repeated muscle injuries. In total days injured only his ligament injury in 2016/2017 and double foot fracture in 2015 matches that.
Martinez has never been this injured before.
Mount has been injured for longer this season than the entirety of his career up to this point.
Quite a few of our players are having the longest injury absences of their careers. For some the increased PL minutes are probably partly at fault, but some of these players barely play and are injured in training. That can't be blamed on lacking the physicial level to compete in the league.