Why is my players always tired

How do I get my players back to full power...my players seem to always be tired
Stop playing and just let them rest or buy health kits or upgrade till you can build a infirmary and that helps them recover faster
Update your stadium to the level 7 and 8 to buy buildings Guild and infirmary and then go into a guild and ask for healing kits and update your infirmary and stop play many practice games