There is an old coaching adage that says a good team is most dangerous after it has hit rock bottom.

Is there any doubt that the Tar Heels are there after the 55-31 shelling by ECU last Saturday? None whatsoever.

Is there any doubt Carolina is a “good team”? Plenty.

So therein lays the key to Saturday’s 12:30 visit to Virginia Tech, which has rebounded from a shaky start to become a good team but remains eminently beatable, even at home.

After two very difficult weeks of game-planning against the triple-option of Georgia Tech and the high speed, spread-you-out attack of East Carolina, UNC defensive coordinators Vic Koenning and Dan Disch have had an easier task this week.

That’s right, easier.

While Virginia Tech has the best total defense in the ACC, perhaps one of the best in the country, the 4-1 Hokies rank in the bottom half of every ACC offensive yardage category. They do have the highest punting average, which means they rely on field position and defense to stay in games and hope their anemic offense can score enough points to win.

The formula worked perfectly in the 17-10 upset of Georgia Tech, an outcome that has left UNC with an opportunity despite its ACC-worst 1-3 record going to Blacksburg.

The defensive game plan is not nearly as difficult this week. Basically contain Virginia Tech quarterback Logan Thomas, who is ninth in the ACC in total offense but first in number of plays involved. Besides handing the ball off to Trey Edmunds, who averages 70 yards a game, Thomas is Tech’s offense.

The 6-6 redshirt senior leads the ACC in pass attempts (159) and is second to Carolina’s Bryn Renner in pass completions (84 to Renner’s 91). But Thomas is not in the top 10 in total passing yards, which means he doesn’t throw the ball downfield very often and/or very well. So, without the so-called vertical passing game as a major threat, the Tar Heels can afford to jam the line of scrimmage on the Hokies and contain Thomas’ ability to escape for long gainers.

That’s why, with far better execution than the last two weeks and fewer damaging penalties, Carolina has a real chance to spring the upset at Virginia Tech, where the Tar Heels last won in 2009. And if that happens, they will have 12 days to prepare for Miami coming to Chapel Hill on October 17.

Despite widespread criticism this week from an angry fan base, Koenning and Disch know what they are doing. And they know the season is on the line the next two weeks against the Hokies and Hurricanes.

The players are embarrassed over their performance in the last three halves of football, and the opportunity is there to shock the world and put themselves back in position to win the Coastal Division of the ACC – as strange as that may seem and sound.

The Tar Heels can score at will on Virginia Tech, perhaps as many as 28 points. Holding the Hokies to less than that is not impossible; in fact, it’s probable. So that’s why the schedule, at least, falls in Carolina’s favor.

A team at rock bottom that has the weapons on offense and nowhere to go but up on defense, playing on the road where no one expects them to win.

That’s a pretty good formula for an upset.