Be able to run the ball. Napier's teams could do that so well. If you can control the clock, you can close out games. We protected a bunch of leads by keeping the other team off the field with crazy long drives at the end of games where we just kept converting, kept converting. 
Defense needs to be better too, but a hallmark of the Napier close game was running the ball. I'll never forget that stAte game from 2021. Protected a 1-point lead with a 20 play, 90-yard drive that ran out the clock. Took over 10 minutes.