Midway through the season, there have been obvious ups and downs for the Penn State football team.

Starting the season with a win over Central Florida in Ireland and winning the next three to begin 4-0? Up.

Losing the next two games against Northwestern and Michigan, teams that were a combined 9-18 in their last 27 contests, including 5-15 against the Big Ten? Way down.

Regardless of how things have played out, there has been one constant on this year’s squad. No, it’s not Christian Hackenberg’s arm, Bill Belton’s feet, or DaeSean Hamilton’s hands. And it certainly hasn’t been the saloon doors masquerading as the offensive line.

It’s Penn State’s dominant defense, a unit that ranks fifth in the country and first in the Big Ten, allowing only 283.3 yards per game.

It all starts with Penn State’s front four. Starting defensive linemen Anthony Zettel, Deion Barnes, C.J. Olanyian, and Austin Johnson have wreaked havoc on opposing offenses, particularly against the run. The rushing defense ranks second in the country, surrendering a paltry 60.83 yards per game and a ridiculous 2.01 yards per carry, the best mark in the nation. In fact, Penn State’s only given up six plays of 30 or more yards the entire season.

Just what makes this team so good against the run? According to defensive coordinator Bob Shoop, it’s because Penn State has players who are committed to stuffing the opposing ball carrier.

“We have guys who understand the defensive concepts,” Shoop said Thursday on a conference call with the media. “They maintain their gap integrity. The front seven is a group of guys that really tackle well.”

“I think our front seven is legit,” he added. “We’re very, very committed in the defensive plays that we call on first down and second down, to calling defenses that are designed to stop the run.”

Shoop also mentioned the brilliant play of middle linebacker Mike Hull as a big reason for Penn State’s success on defense. He called Hull an “eraser,” and praised the senior for his ability to make plays up the middle and on the perimeter. After his 11 tackles and 2 tackles for loss against Michigan, it’s easy to see how big of an impact the veteran linebacker can have, and Shoop thinks he should be getting some more recognition for it.

@BednarikAward..Really Bednarik Award?? No Mike Hull? Watch a game..any game..as good a LB through first half of year in the game..#LBU

— Bob Shoop (@Coach_ShoopPSU) October 15, 2014

“Mike Hull is the straw that stirs the drink,” Shoop said. “Anybody who knows anything about college football should watch, and that guy’s just really played as good a middle linebacker as there is in the country.”

“The guy has an understanding of the defense as well as any player I’ve ever coached.”

While the defense has been impressive, there are still areas that need improvement. The Lions are allowing conversions on third down at a rate of 34.83 percent, good enough for 39th in the nation, but well below the spot a dominant defense should be. Shoop, who believes stats tell a story and disagrees with the old adage that they’re “for losers,” said the team has done a good job on minimizing gains on first and second down, but against first-rate opponents in the second half of the season where the margin for error is minimal, the defense needs to be better on third down.

One of the ways to improve, Shoop said, is to bring extra pressure on blitzes, forcing the opposing quarterback to make quick decisions under duress.

“We can get home when we bring three or four guys up front because they’re really good pass rushers,” Shoop said. “But when we’ve defended and played coverage, teams have made conversions on us on third down.”

For Penn State to have any chance of beating the Buckeyes, the Nittany Lions must continue to play well against the run, especially with dual-threat quarterback J.T. Barrett rapidly improving as the signal caller for Ohio State. After completing only 31 percent of his passes and throwing three interceptions in an ugly home loss to Virginia Tech, the freshman has completed over 75 percent of his passes for 909 yards and 14 touchdowns to only one interception in the Buckeyes’ last three games.

“They’re playing with a lot of confidence, they play with tempo,” Shoop said. “They can speed it up, they can slow it down and they recognize mismatches and they have a great idea of who they are and what their identity is on offense. It will be a tremendous challenge for us.”