By FAR the best way to do this requires 4 controllers (as in REAL controllers, the Guitar Hero stuff won't work quite as well), and two people. Doing it by yourself is not possible.
Put three of the controllers on one team (the team doesn't matter, I picked Kazakhstan because their stats were garbage.. also, jagshemash!), and the other controller on the other team (my friend picked Pittsburgh, just because). Now, be sure to designate one of the controllers on the losing team as the Goalie (you do this by pressing X after choosing your team, and you'll see a "G").
As soon as the game begins, IMMEDIATELY get two guys penalized (just slash the other player with the Y button). Now you should have TWO player controlled guys, an AI, and the goalie, which is controlled by the third guy. Here's the trick. One controller goes to the other player's net; just leave his ass there.
NOW, your friend (or you) gets the puck, and goes where the other guy is. Bring the SECOND controller over here as well, and at this point, the AI guy on your team should still be hanging out in front of your goalie.
This is where it gets tricky.
Whoever is getting the achievement MUST beeline towards the goal now, WHILE the other guy switches players (RT) to the guy in front of the goal. This way the achievement guy WONT be harassed by AI. The challenge is that your guy must turn around being the achievement guy pretty quick, and dive (RB + LB) into him as he's on a breakaway. He should NOT be winding to shoot the puck, and MUST be moving.
It DOES take practice and timing. But don't worry, you have to wait for the game to end to get the achievement anyway, so just keep at it.
If you do it right, you'll knock his player down, and he'll (or you'll) be rewarded with a penalty shot. Simply take the controller that was designated as the goalie, move him to either the right or left of the net as far as possible, and it's easy to make the goal.
The achievo pops at the end of the 3rd period.
NOTE: Do NOT change any settings during the game. I got the idea to change one of my controllers to the goalie in-game, and I got NO achievement.