Easy achievement. Start up a Road To Glory and Create a Player. Set the difficulty to Freshman and simulate the high school season from the start to signing day.
Once the season is over, select a school to play for that says your position is "2nd string". To be safe at this point, save your RTG and turn autosave off.
Go into practice mode during Week 1 and you need to get the amount of coach trust points to be eligible for a position battle. If you achieve the required amount, save your RTG and play the Week 1 game. DO NOT sim before the game, go into the game and you can supersim to the end from there. Once you enter week 2, you should be ready for a position battle.
Participate in the position battle and if you achieve the required number of Coach Trust points you should win the battle. DO NOT QUIT ONCE YOU WiN THE BATTLE MAKE SURE YOU FINISH OUT THE NUMBER OF REPS OR YOU MAY HAVE TO START ALL OVER!