In general I sub 1-3 players around 60 mins and then all the rest until 70th minute. Players don't get rating if they are subbed on after 75th and I think it's the same for expected playing time.
I don't save any for cases of injuries unless it's an important cup game or last couple of league games. I've played at least 10 seasons so far, the number of times I lost a player due to injury is 2 or 3. I do have to mention though that I'm very aggressive in keeping the guys fit. Anyone carrying an orange injury isn't selected in the team or is subbed off as soon as I notice it. I also don't play anyone that is "tired" before the game even though it shows nearly full fitness. Plus most of the subs I make are for fitness reasons - whoever is red on fitness at 60th and then 70th minute.
I don't save any for cases of injuries unless it's an important cup game or last couple of league games. I've played at least 10 seasons so far, the number of times I lost a player due to injury is 2 or 3. I do have to mention though that I'm very aggressive in keeping the guys fit. Anyone carrying an orange injury isn't selected in the team or is subbed off as soon as I notice it. I also don't play anyone that is "tired" before the game even though it shows nearly full fitness. Plus most of the subs I make are for fitness reasons - whoever is red on fitness at 60th and then 70th minute.