Here's how I managed my players health & injuries packs. I seldom find the need to use any medic packs for injuries because

1. I make sure I get players to sit on the bench who are capable of filling in when key players are injured. This helped me during that crazy period where my players were getting injured in almost every game. I had 5 players out at one time and got my reserves to step up and fill in. On some scenarios I play an MC as a winger or a DMC as MC just because it is possible since the positions are similar.

2. I make sure players are at least 75% - 80% condition. If they do get injured it'll probably be only for 3 days. If your player gets injured when they are 60% condition in-game, they will be out for longer periods.

3. Referring back to no 1, not using medic packs for injuries will ensure you are accumulating medic packs daily (from gifts, first aid centres) & not using them. You can probably have > 50 packs without having to use tokens to get them. So when you really need to, you can use the max 15 pack to heal your players (I usually it on my most important player if I had a bunch out)

I think a lot of managers worry about injuries because their playable players are their starting 11 and panic when one gets injured. This should not be the case.