To be a successful QB in the NFL you are one of a select crew of people. You have to have great athletic talent in throwing a football.
If you are a successful QB you have to lead and inspire a group of 50 men. In the military that constantly scrutinizes for leadership, that equates to a line captain at least. Many a second lieutenant, commissioned as a leader is shunted off to other duties, if they can't LEAD men. Cassel seems to have passed that test. There was no complaining and backbiting in the locker room about the kid screwing up, and that he couldn't cut it. Even early in the season when it was obvious to all, he was feeling his way around. Team mates pitched in and helped as best they could. Intangibles and leadership bring that out.
You have to be extremely competitive, too. Some, when they lose the competition, pickup their marbles and go home. Like Gutz did transferring to Idaho State, from Michigan after getting passed by. OTOH, Brady fought for his job against the big time new comer at Michigan, and prevailed. Cassel lost out to Palmer, and Lienart, and even Brady, but he didn't quit. He still aspired to QB the NCAA National Champions at USC. Maybe Palmer or Lienhart would go down or turn bad. He stayed and he competed.
Now the stakes are higher. You can accept a trade to the Detroit Lions and start. You might and probably will get beat up. You might get injured and end your career. You will lose until the talent is better, and pay the price. The Lions 5 year plan can mature, and you can lead a rejuvenated Lions to winning season in 5 years.
Or you can gamble, and compete for higher stakes, the bigger prize. You can compete for the job as Patriots QB. It would be for the best or near best team in the League. Superbowl appearances. MVP possibilities. Winning seasons. Playoffs every year. If you win, you inherit the job as the QB of the building Juggernaut of a renewed dynastic football power.
Sure you're is going against the other guy, former MVP. But you have some cards of your own to play. The other guy is 6 years older, beginning the downside of his athletic career. He has maybe 4 more good years. You have ten years to go, and you haven't yet reached the mark to how good you will be. In a comparison of pure arm strength, you probably win. He is accurate, but so are you. The other guy was never as mobile as you are. Your mobility is a weapon that you have shown can be exploited too. The other guy was severely injured, and may never be the same. As was said he had little mobility before, maybe he won't have enough to succeed now. In the service, many fearless guys, after getting hit, just seem to lose something, some fire in the belly, and are intangibly never the same, even though they are completely healthy. Could this be the case?
The Judge of who wins this competition is not a stranger. Cassel knows him. He is bloodlessly and ruthlessly, realistic, and interested in what will give him the best chance. He has a track record of selecting the best player that can help him win. He cares not for yesterday, and is focused on today and tomorrow. Belichick sat down two fan favorites for the younger guy, who he judged was better for today and tomorrow not based on yesterday's headlines. He is ruthlessly fair.
Would you take a two year deal and $20-25 million guaranteed; and sit down, play cards, and compete?