Factors such as playing a rival team (ie arsenal and manchester), weather, home/away setting, previous team performance, fatigue, etc should all contribute to change a specific players performance from game to game. For example, if the weather is rainy, a players shooting accuracy should go down accordingly for that game, but the keepers handling ability should also drop. Or, if the players are really psyched for like a World cup comeback (ie if Brazil had to play france again in this WC2002), the team that has more incentive and passion to win should have the whole team's stats bumped up accordingly..
This type of fluctuation of stats would create a superior game in my opinion :)

Football! :jambo: I thought of something else as well. The postion a team is in their league should effect their perfomance. For example if a team like ARSENAL is top of the table their team will have a lot of confidence so they will play better. And if a team like MANCHESTER UNITED is bottom of the table, their performance will be crap as they will have not much confidence because they will be in the relegation zone! GOING DOWN TO DIVISION 1! lol