For this achievement you are required to play a full match as a goalkeeper without any assistance from the game.
To do this you will need to switch off the assistance which is set to semi or assisted by defult. Do this in the main menus by going to My Fifa 11 > Settings and Profiles > Controls > Xbox 360 Controller.
Once there scroll down until you get to Save Assistance and change it to MANUAL. This will mean you will have to physically save any shots, the computer wont give you any help.
Now go to Kick Off > Be a pro Goalkeeper and you can choose any teams. From here you just need to finish the match, doesnt matter what the score is.
Once the game has finished, the achievement is yours.