This requires you to score at least an "A" grade not just overall but in all three catagories; Stats, Teamplay and Position score. The difficulty has to be set on at least Pro difficulty but you can adjust sliders accordingly. MAKE SURE YOU TURN OFF THE AUTO SAVE!
You can use either your own Be A Pro character or use someone already in the NHL using NHL Be A Pro. Pick a player, get through the introduction and all the way to the first game. Now, save your profile and season. At this point, sim the first game and if you get all A's in EVERY catagory play the next game. It doesn't matter how well you do or if you are the goalie how many shots get in. The achievement should pop just as the game completes. If you don't get all A's simply reload your file and try again.
I would like to add that after simming your all A's grade for your game, DO NOT SAVE just play the next game. I could have saved myself the headache had I just played the next game instead of saving it.
A more in-depth explanation from Jrath05 can be found here.
Thanks to xMidget_Furyx and Jrath05 for the clarification on this achievement.