I've currently been working on the players shooting ability at goal for the computer opponents. When testing the game it's all too easy to beat the computer by a large goal difference as their shooting ability isn't up to scratch.
By messing around with some variables I've given each team different shooting abilities. Some will still be crap at it but others will shoot at much tighter angles and away from the goalie. This has worked well and when playing I've actually lost a few games to the computer.
So I've now got some really tough teams to beat who are fast at running with the ball, have great shooting ability and are good at passing. I was toying with the idea of displaying each teams stats on screen so you could work out who was the better teams, but I think the fun of a football game is working out which teams are good and which ones can easily be beat.