The problem with Romo wasn't just that he had poor showings in big games. It was also the timing in those games that he made the poor plays. You can have 2 QBs throw for over 300 yds with 3 TDs and 2 ITs and consider one to have played well and the other to have choked. If the ITs come early there is still time to make up for it (and depending on where they took place they may only cause you a possession). However, it they come late in the game they can seal your fate. Romo was notorious for turning the ball over in the 4th quarter and in a way that often led to the other team scoring.