Warning: this achievement is GLITCHED.
EDIT: as of 5/1/17, the achievement has been patched and it is now obtainable. Original issue outlined below is now obsolete.
You're supposed to get it right before you play your first playoff game. A cut scene plays where your old coach hands you a gift. Achievement is supposed to pop afterwards. It would have been nice if someone here had posted this earlier, seeing as how some of you have 5,000,000 fans you guys clearly would have known this shit already and could've posted about it here.