This achievement can be unlocked simulating every game up to the regular season. I would suggest creating either a Center or a Winger, keep the difficulty on Pro or lower, and to select a decent team that has a shot at the Cup for later on.
After simulating all the preseason games up until to the Regular Season, and you should unlock the You're Not Cut achievement. If for whatever reason you don't make the team, simply quit out and try again. I made it on my first try.