Injured reserve

How do they determine IR. I had a player that was injured for 2 weeks that I could place on IR, and oner for 10 weeks that I couldn't.

I could be wrong but I think once a player is listed by the game engine as OUT, he is eligible for IR. Doubtful listings usually mean can not be placed on IR.

Out usually only happens when health bar hits zero

you're not wrong, raider :)
Too clarify: the injury rating must ALSO be at (0). COncussions - though non-zero, CAN be out as an player heath designation with a non-zero injury status while also being ineligible for IR.

THIS ↓↓↓
Personally, I'd suggest changing the injury value requirement 30 and below.
I would also really like if players placed on IR in MFN could have the ability to "Designate A Return" after 4 weeks - as the NFL does.
THAT ↑↑↑

Hopefully - a near future update.

I've put a player on IR only for them to quickly recover, as well as not having put an IR eligible player only for that player to take the entire season to get to a +50 injury rating.

Anyway That's MFN IR explained (soon to also be a History channel mini-documentary).
Hope we helped :)

I'd like to see IR with eligible to return, maybe limit to once per team per season...going to post this in suggestions