I constantly disconnect from the servers in the second round of the daily knockout in matches when i am in the lead. I am not lagging in the game and i still disconnect. It's happened over four times. I'm very disappointed in the server quality.
FIFA is a peer-to-peer to game, so you're not actually connected the servers when playing an opponent. You're likely losing connection from your opponent.
You may look at opening up your ports to help improve your connection.