I don't normally bother that much with condition. I try to start a game with every player on green, but I've occasionally started with a player on yellow due to training, or playing in an earlier match.

I never run the players intentionally below around 50%, but I have no problems starting players who are around 70-75%. Performance wise I can't say I feel my team has really suffered as a result.

I try to play at least 3 friendly games within my squad of 22 as well as my competitive games each day. I have stopped training players, simply because they get injured too easily - and by playing friendlies you also get extra blue/red/green packs as well as money from the gate. With wages increasing as you go up levels, bringing in that extra revenue is good in my opinion in keeping my finances ticking over.