Interesting. My draftee got injured after 46 minutes of play. That said, my current injured player got injured after only 21 minutes of play, hence it might also not be stamina.
I guess more data might help.
Tbh I would have just dismissed it as "doctor is too low" but the fact that I already have a level 6 doctor and still get a 2 week injury, that's definitely not the case. I mean, I understand injuries happen. They happened throughout my time with a level 6 doctor as well, except that they always heal after the game. This is the first time I'm seeing lingering effects (and up to 2 weeks). I just wonder how long it would be had I not have a level 6 doctor.