I was able to get this achievement by going to quick games in the NBA today menu, and making custom settings.
Go to NBA Today
Press B
Pick Quick Game
I used a custom roster but any should work
When the game starts press menu button and go into options
Use the RT button to scroll to the CPU settings
Use custom settings and drop all the CPU stats to 0
Play the game and let the timer go off
Just to be safe I sometimes tweaked the settings to allow the CPU to score some 3PT shots. This is so I was 1 pt behind. When the time comes and there is less then 20 seconds left on the clock, make sure you have the ball. If you set all of your shot stats to 100 (opposite of what you did to the CPU), try to score just as the timer runs out. I made it just at 1 second, and the achievement popped.
If you need any clarification, just make a comment.