Liberty led 22-21 with about 6 minutes left in the third quarter before Williams found Mack Hollins for a 33-yard scoring pass. Williams later scored on a 15-yard keeper and backup Mitch Trubisky followed with his first career TD pass for a 49-22 lead with 2:06 left in the quarter.
That stunning turnaround couldn't have happened without the maligned defense - perhaps UNC's biggest question mark coming into the season - forcing three turnovers in the third and setting up the sputtering offense with short scoring drives against Liberty.
For a time Saturday night, it looked as though the Tar Heels were flirting a surprising home loss to a championship subdivision team. But the defense allowed just 53 yards in the third quarter to provide a needed spark and finished with six takeaways for the game.
As for the offense, Williams got the start after battling with Trubisky for the starting quarterback job through preseason camp, though the team rotated them for much of the night. Williams shook off two badly thrown interceptions and finished with 169 yards passing with two TD throws to go with two scoring runs - the first one giving UNC a 21-15 lead with 28 seconds left in the first half.
Todd Macon ran for two touchdowns and D.J. Abnar added one for Liberty, a Big South Conference member playing a ranked bowl subdivision opponent for the first time. Jacob Hagen also returned a fumble 27 yards for a touchdown and the 22-21 lead with 9:25 left in the third before the Tar Heels finally kicked into gear.