Head coach Larry Fedora hinted at Heffernan's emergence during the final days of training camp.
"He has done a nice job," Fedora said in August. "He's really, really showed some things and is going to be a contributor. You see it sometimes out of Travis Hughes and P.J. (Clyburn). They have all kinds of ability but they need to be more consistent."
With North Carolina trailing Louisville, 36-7, early in the second half on Saturday, Heffernan ignited the defense with a 10-yard sack of quarterback Teddy Bridgewater on 2nd-and-7. Five plays later, he tackled Jeremy Wright on first down and then stuffed Senorise Perry on 4th-and-1 at UNC's 20-yard line.
The Tar Heels scored on the ensuing possession, sparking a 27-3 run that fell four yards shy of an improbably comeback.
Heffernan finished with nine solo tackles – four more than the next closest defender on either team – to go along with three assisted tackles and a sack.
"Tommy moved in there and did a great job," Fedora told reporters during his weekly press conference on Monday. "[He] was one of the few bright spots that we had defensively. He played really well, probably the best game he's ever played. I don't know if he's ever played that extensively, but he played really well for us, especially moving into that role the way he did this week."
During his postgame interview, Heffernan preferred to talk about his team's second-half revival over his own play.<> "I think it shows what this team can potentially do," he said. "It shows that if we would have played half as hard as we did in the second half in the first half, then we would have won the game. My hat's off to Louisville – they are a great team – but it just shows what we are capable of when we are fighting."
A constant theme for Fedora has been the acceptance of adversity as a learning tool, and there's few better examples on the roster than Heffernan.
He red-shirted in 2010 after tearing the labrum in his shoulder and needing surgery during training camp. He left the team for a short period that fall while dealing with the tragic death of his best friend before returning to play in six games in 2011.
Heffernan, whose father David played offensive tackle for the Miami Hurricanes in the early-1980s, earned a scholarship from former UNC head coach Butch Davis in May of 2010. Fedora extended his scholarship this summer for the 2012 season.
Heffernan is slated to start against East Carolina on Saturday.