This trophy is now unobtainable due to the servers being closed. The servers finally went down on the 28th February 2014.
Before the servers were closed what you had to do to get the trophy was use a player for 100 games in the ultimate team mode. The best way to go about this in my opinion is buy a good player who will fit into your teams chemistry and way of playing, preferably a gold player and use him in every game you play.
You will need to apply some contract cards to the player as he will not last 100 games without them. Being a gold player you will only need 5 or 6 rare gold contract cards before he will be all contracted up until what you need him to be. He can only be contracted upto 99 at most so you will have to do it in two goes at least.
You will also need to take into account fatigue. He will not last 100 games in a row without getting run down and injured. I chose to swap the player in and out of the team but if you don't want to do that you will have to buy some fitness cards. If you use this method you will need lots of these cards as the fitness doesn't last long.
If you do all of this the trophy will come soon enough. If you love Fifa and ultimate team this would have come with just playing the game, if you don't then it would have been a massive grind as the games were 12 minutes each.