Do injuries Linger? Like if my running back has had a bad injury ( Over 8 weeks or so ) will he be subject to rehurting it for a few more weeks later in the season or his career after it heals?

I've no idea on your question but in one of my leagues I traded for an OL that played almost 1400 snaps last season (pre, regular and post season) without getting injured, 35 snaps in his first pre-season game for my team and he's injured for three weeks

The players conditioning has an influence on injuries. Pre season....especially if they miss camp will start with real low conditioning.

The injuries that carry over to the next season could take small points off ratings and the “serious “ do add to early retirement.

Still conditioning and a players size are the strongest influence besides snap count and luck.

Fatigue settings during a game have a big impact on injuries by keeping players fresh and distributing snaps.

The default settings are, like most default things, awful. Your RBs are going to get 400 carries a year. Dropping these down to 40-45 and keeping multiple RBs on hand allows you to go to a committee approach while letting your #1 do the most damage.

If you can handle the override settings, keep a dedicated 3rd down back on the bottom of the depth chart to sub in to catch passes. Let him get 40 carries and 40 catches over the course of the season and watch him get 400-500 yards receiving and 4-6 TDs without ever running for 100 yards in a game.