The the last few days and first few days of a Season seem to be worst for injuries.

Playing a guy one spot out of position won't hurt much, sometimes the player likes it and gets a 7 or 8.

Having the best turf possible does help lessen injuries. Having your facilites built up will give you more green and red packs.

5 days or 20, still 15 red packs to heal either way.

Often I let less than 5 day injured players heal naturally without the packs unless it is a very important player, and use greens on the guy who gets to play every match. When I have more than 3 guys hurt I consider selling the one I love least and buying a cheap old guy until I can replace with similiar.