“We’ve hit some skids and allowed some big plays,” first-year Virginia defensive coordinator Jon Tenuta said. (Sabrina Schaeffer/AP)

Virginia hired defensive coordinator Jon Tenuta this offseason because it thought he could solve an aggression problem. Coach Mike London and administrators were right.

A year ago under Jim Reid, the Cavaliers created just 12 turnovers the entire season — only three Football Bowl Subdivision schools created fewer — and ranked outside the top 75 in the country in terms of sacks and tackles for a loss. But in all three categories, the Cavaliers have shown marked improvement this year.

If only creating a powerful defense were that simple.

A look at national statistics over the past two years revealed that Virginia has slipped in almost every other significant defensive area heading into its season finale against Virginia Tech, including points and rushing yards allowed, red zone defense, third-down defense and total defense.

“I just think it’s kind of a roller-coaster ride,” Tenuta said Tuesday in his first public comments since the days after Virginia’s season-opening win over BYU. “Sudden change has really killed us this year. We haven’t done a great job in sudden change. I mean, honestly, our red zone defense is part of that aspect, and then obviously we haven’t created as many turnovers or had as many negative plays as I was hoping for. We’ve hit some skids and allowed some big plays.”

Aside from a schedule that included offensive juggernauts like Oregon and Clemson this year, injuries to key players have exacerbated the unit’s weaknesses. The Cavaliers haven’t had defensive tackle Brent Urban, their best 2014 NFL draft prospect, and top cornerbacks Demetrious Nicholson and Maurice Canady on the field together since the team’s 14-3 loss at Pittsburgh on Sep. 28.

The Cavaliers got Urban and Canady back from injury in Saturday’s 45-26 loss at Miami, and it was no coincidence Virginia turned in its best defensive performance in weeks, final score notwithstanding. After allowing nearly 500 yards per game the previous five contests, the Cavaliers gave up just 304 as Miami completed less than 50 percent of its passes and averaged 3.6 yards per rush.

Canady confirmed this week he missed three games after suffering a kidney laceration when the Cavaliers lost to Duke on Oct. 19. Nicholson is out for the season after a turf-toe injury suffered at Maryland on Oct. 12. Urban, meanwhile, was out because of a high-ankle sprain suffered against the Terrapins, but tallied two tackles for loss in his return to the starting lineup this past weekend.

“I was confident I would make it back,” said Urban, who recently accepted an invitation to participate in the 2014 Senior Bowl in January. “I feel I was at the level where I could play at the ability I’ve been playing early in the season.”

Virginia Tech’s coaches have noted the 6-foot-7 Urban completely changes how Virginia plays defense, and Tenuta confirmed as much when he spoke with reporters Tuesday.

“The total package comes into play when everybody is there,” he said. “When you’re missing certain pieces of the puzzle, I mean, you’ve got to go to the simplistic aspects of it. Obviously haven’t been able to pressure and do a lot of what I really like to do, but you’ve got to do what your kids can do.”

On Saturday, the Cavaliers will have to make do without safety Anthony Harris during the first half. The junior leads the country with eight interceptions this year, including at least one in each of the past five games. But he was ejected from the Miami game for targeting and an NCAA rule instituted before this season mandates he miss the first half this week as a result.

Replays indicated Harris did not lead with his helmet on the play, but the penalty stood even after an official review. Virginia’s coaches and players were not pleased about it, both publicly and behind the scenes. Coach Mike London noted he spoke with ACC head of officials Doug Rhoads about the call and expected a statement from the league at some point this week.

Harris was diplomatic about the situation.

“It’s just one of those plays where you can’t really control what’s going on. The game’s played at a high speed, so sometimes things are gonna be close,” he said. “But I don’t view myself as a player who targets players or anything like that. I wasn’t offended by the call. I know they have rules in place for safety matters and that being said, if you have to make a call, sometimes it may be close or not. But we have to make sure players are safe out there on the field.”

With Harris not on the field, Tenuta said Virginia would likely move Canady to safety during the first half. Because of injuries in the secondary, the Cavaliers have been forced to use freshman cornerback Tim Harris more than they’d like and he has been exposed at times.

It’s the sort of domino effect that has derailed Virginia’s defense for the better part of two months now.

“We have not played the ball well. We’ve had too many balls thrown over our head,” Tenuta said. “You just got to keep working at it. We’re going into our last game and we’ve got to go into spring ball and change some things or find out what guys do the best. … It’s hit or miss, and when we hit on all cylinders, we’re pretty good. And when we don’t, too many big plays and that’s what hurts you, especially in the back end.”