EA SPORTS FC™ TeamHi @rrancan,
There's no way for your opponent to change the stamina of your players. Check if you changed tactics during the game, switching to an offensive mentality. if you did, your team pressed your opponents and lost stamina very fast during the game. Try this strategy only in critical circumstances and for a short period of time.
Currently there is a cheat that makes your players get tired in the first half without any pressure tactics. You don't need to be very wise to find it on the internet. In fact, the most common thing in the game today are cheaters. I have more than 22 videos recorded of opponents using them.
