Past is history. It has no impact on the present or future other than what we can learn from it.
J.T. is NOT a freshman, he is in his second year in the program and has had the benefit of two Springs, as well. He is actually farther along in his development than Braxton was in 2012 because of the coaching he has had.
The O Line is better (better talent, more depth, more time in the system) than the one that went 12-0 in 2012, and the Defense should be solid (some have suggested it might be the best in the country).
Yes, the loss of Braxton potentially puts the Virginia Tech, Cincinnati, and Penn State games in play, and it makes MSU a real challenge, BUT ...
The VT game, because of the style of defense and the talent in the defensive backfield (best in the country?) should tell us how the rest of the season will go. If we put up 27 or more points against VT, I think we should win the B1G and be playoff bound. If our offense struggles, then we will probably end up 10-2 or 11-1 and go to a January 1 Bowl.
Since all is speculation, I am going to sit back and enjoy the season, focusing on Navy and VT to give me a barometric reading for prediction purposes.