CHAPEL HILL, NC – It would be easy to dismiss North Carolina’s upset loss to Clemson on Tuesday as the result of a post-Duke hangover.

Or the missed wakeup call that led several of the Tar Heels oversleeping their pregame naps and the absence of injured wing Seth Trimble.

Or even the urgency of a Clemson team that desperately needed a resume-building win to stay off the NCAA bubble.

All those things did contribute to the 80-74 result that gave the Tigers only their 2nd victory in 62 trips to play basketball in Chapel Hill.

But there’s one other, much more subtle factor that also weighed heavily on both UNC’s subpar performance and the outcome.

And it should be viewed with concern by coach Hubert Davis, his players and their fans.

Not only did Clemson hand them their 2nd loss in the past 3 games, cut their ACC lead over Virginia and rival Duke in half and most likely knock them out of the top 5 in the national polls, Brad Brownell’s team also may have provided the Tar Heels’ remaining opponents with a roadmap for beating them moving forward.

In order to take them out of the zone they’ve been in lately, simply throw a zone at them.

OK, maybe Duke’s Jon Scheyer tried it first last Saturday, with some degree of success. But he didn’t stick with it.

Brownell did. For extended periods. Each time sending UNC straight into the Twilight Zone.

The defensive adjustment threw the Tar Heels completely out of sorts and allowed the Tigers to regain control whenever their coach decided to pull it out of his bag of tricks.

“We mixed in some zone and I thought it helped us at times,” Brownell said afterward.

Did it ever.

The Tar Heels were well on their way to recovering from the 15-2 blitz Clemson hit them with to start the game when Paxson Wojcik sank a 3-pointer to cut the margin to 23-17 at the 10:10 mark of the 1st half.

With the lead down to 6 and the Smith Center crowd sending out a wave of sound loud enough to shake UNC from its early doldrums. Brownell decided it was time to change things up and switch to the 3-2 zone.

It paid immediate dividends.

The Tar Heels in general and freshman point guard Elliot Cadeau in particular looked unprepared to handle the switch. Taken completely out of their rhythm, their next 5 possessions consisted of a Harrison Ingram turnover (on a steal by Dillon Hunter), rushed 3-point misses by Wojcik and Ingram, 1 of 2 free throws by Wojcik and a missed jumper in the lane by Cadeau.

Clemson responded with a 9-1 run that helped it regain some separation.

It was more of the same in crunch time.

When Ingram hit a 3-pointer shortly after returning to the court from a cramping issue to tie the score at 70 with 4:17 remaining – the first time UNC had pulled even since the score was 2-2 – the outcome felt inevitable.

And frustratingly familiar to the Tigers.

That is, until Brownell went zone again. And the Tar Heels’ momentum once again came to a screeching halt.

Armando Bacot had the ball stripped from him by Jack Clark. Cadeau, who went 2-of-6 from the floor with only 1 assist and 2 turnovers, then committed an offensive foul trying to drive into the teeth of the Clemson defense. RJ Davis missed a 3-pointer and Jalen Washington turned the ball over attempting to pass the ball out of a double-team.

Just like that, Clemson was back up by 7 and the game was decided.

“You have to execute on the offensive end,” UNC coach Hubert Davis said afterward. “Those are things down the stretch that you just can’t have.”

While the late-game meltdown was out of character for Davis’ 3rd-ranked team, especially given its history against Clemson in Chapel Hill, it wasn’t necessarily a surprise given the Tar Heels’ inefficiency on the rare occasions they’ve seen zones this season.

According to the number crunchers at Synergy.com, UNC is averaging .96 points per possession against man-to-man defenses, a rate that’s among the best in the country. But in its 58 possessions against zones before the Clemson game, it was averaging just over 0.9 points per possession.

Against Clemson’s zone on Tuesday night, the Tar Heels averaged just .76 points per possession — 23 possessions in total.

It’s not as if the Tigers are a vintage Jim Boeheim Syracuse team when it comes to use of zone defense.

Prior to this, Brownell had only used the zone on 48 possessions all season. More than half of them, 27 to be exact, came in a win at No. 16 Alabama all the way back on Nov. 28. Give Brownell credit for winning the battle of Xs and Os.

UNC’s difficulty in handling the zone against a team that doesn’t normally play zone should serve as a wakeup call for the Tar Heels – hopefully better than the one that some of their players slept through on Tuesday – to start working on attacking it better at practice.

Because you know others around the ACC, starting with Saturday’s opponent Miami, were watching.

And they’re bound to see it again.

Saturday Road’s Neil Blackmon contributed to this column.