The mythology is that old-time players, who did not lift weights and knew nothing about nutrition, had mercilessly short careers. And that today’s players, who condition themselves year-round — often with the help of private trainers, the most up-to-date scientific methods, nutritionists and massage therapists — play longer and have more years of peak performance. It makes sense. It’s also not true.Interesting piece. But I think there is something missing in it, which is the role that injury plays, particularly injury that is not reported in the papers. One has the impression now that Jeter used to be able to perform at a high level even with minor injuries. But now he can't.