About half of those 9 points could come from playing better in the red zone. TCU scored 4.2 points per red zone possession*; 113 FBS teams averaged more. An extra point per possession in the red zone would add an extra .32 points per possession across all possessions and 4.4 points per game (13.8 possessions/game*.32 points/possession = 4.4 points/game). That number is even bigger if we assume Pachall gets TCU into the red zone more often than Boykin.
The defense did a lot of things well. They held opponents to 5.1 plays and about two minutes of game time per possession. Opponents averaged only 24 yards per possession and touchdowns on 16.8% of possessions. They completed fewer than half of their pass attempts and averaged less than 4 yards per carry, and converted only 31% of the time on 3rd and 4th downs. They got sacks on only 6.3% of pass attempts, but picked off 4.5 passes out of every 100. They were a step behind Alabama and Florida in terms of the the country's best defenses but solidly in the second tier with Stanford and Michigan State.
The TCU defense is an institution, and a very experienced institution this year. They should get even better with a year of Big 12 offenses under the belt, especially as Big 12 offenses take a step back. And that could make a real difference on the scoreboard. Alabama, for example, allowed .86 points per possession. It's almost impossible to drive that number down even if the defense gets better. TCU, on the other hand, allowed 1.46 points per possession. If they can bottle up a few more explosive plays and the offense can give them better field position to work with, that number could fall by a few tenths of a point, which over the course of a season adds up to a couple extra wins.
But the real progress will come on the offensive side of the ball. If Pachall returns to form, TCU could easily lift its points per possession from 1.86 to 2.3 or 2.4. If that happens, TCU will be competing for a Big 12 title and in the running to lose to an SEC team in the final BCS title game. They have a chance to make a real statement against LSU on August 31.
*This is an offensive metric and so excludes the impact of special teams play. In case of a field goal attempt, offenses are awarded the average points scored based on the distance of the field goal.