(STATS) - Seventh-ranked South Dakota State is off to an impressive start behind the Missouri Valley's top passing attack, but isn't sure who will be in command of that high-powered unit come Saturday. It's one of the reasons the Jackrabbits (4-1, 1-1) will be slight underdogs when they visit No. 11 Youngstown State (3-2, 1-1).

Junior Zach Lujan started the first four games and ranks sixth nationally with 311.0 passing yards per game, but suffered an ankle injury late in the team's 28-7 loss to North Dakota State on Oct. 3 and still may not be 100 percent.

Freshman Taryn Christion impressed in his collegiate debut last week in Lujan's place, completing 15 of 24 passes for 221 yards and a touchdown while running 16 times for 99 yards and another score in a 24-7 win against Indiana State, earning STATS National Freshman of the Week honors.

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A Sioux Falls native, Christion was a highly regarded recruit but couldn't beat out Lujan for the starting job in the preseason. With both having played well and Lujan's health a concern, it begs the question - who gets the nod this week?

"It's up in the air right now," coach John Stiegelmeier said. "In my 19 years as a head coach, if a starter is injured and loses his spot and comes back healthy, he's automatically the No. 1 guy. So right now our No. 1 quarterback is Zach Lujan."

Bo Pelini's Penguins had issues containing a dynamic quarterback in last week's 31-29 loss to Illinois State, surrendering 11.8 yards per pass attempt and 90 rushing yards to Tre Roberson.

"I imagine we're going to see both (quarterbacks) this week," Pelini said. "You just have to be prepared to react to whatever they do."

Youngstown State nearly rallied late Saturday in its bid for a fourth consecutive victory, when Martin Ruiz caught a 13-yard TD pass with 32 seconds remaining, but the Penguins' two-point conversion was unsuccessful.

Regardless of who's throwing the football, the Penguins will have to be cognizant of Jake Wieneke, who ranks second nationally with 131.4 receiving yards per game.

Pelini has cultivated a dominant defense quickly in his hometown, however. Youngstown State is holding opponents to 268.4 yards a game, the fourth-fewest in the FCS.

"I think we're making some progress. We're not where we want to be," he said. "I think there's some things we can do better in every phase. We've just got to keep working hard."

The Jackrabbit defense comes off of a strong performance of its own with six sacks against the Sycamores.

Should the game come down to turnovers, South Dakota State may hold an advantage - the Jackrabbits haven't had a giveaway in four of five games.

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LEATHERNECK BREAKTHROUGH?=

Only three undefeated teams in league play remain after just two weeks of conference action, and one of them is surprising Western Illinois.

The Leathernecks (3-2, 2-0) are the lone unranked team among the Valley's six schools with at least three wins overall, though they'd surely break into the poll with a victory Saturday at No. 12 Northern Iowa. Their 2-0 start in league play is their first since 2010, also the last year in which they reached the playoffs.

"If you're going to have a chance to compete in the top of the league, you've got to beat good teams," coach Bob Nielson said. "I thought a win over Southern Illinois and South Dakota were good wins. But now you've got to go on the road ... Northern Iowa's going to be a different type of test in a lot of ways."

The Panthers (2-3, 0-2) have dropped three of their first five for a second straight season, but the record may again be misleading. All three losses were on the road, including two against top-four teams North Dakota State and Illinois State by a combined 11 points, as well as a season-opening defeat at Iowa State.

Northern Iowa won six of its final seven regular-season contests last season - including a 27-13 victory at Western Illinois - and advanced to the second round of the playoffs.

"I just think this football team has a lot of upside right now," coach Mark Farley said. "We've got to get that momentum, we've got to be a little more consistent.

"We've got to have the outcome start falling in our direction so it pays off in the end."

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STILL PERFECT=

The other 2-0 teams in Valley play are No. 2 North Dakota State (4-1) and No. 4 Illinois State (4-1). Both are heavy favorites to improve to 3-0 with the Bison hosting South Dakota (2-3, 0-2) and the Redbirds traveling to Missouri State (1-4, 0-2).

Though North Dakota State escaped UNI on Carson Wentz's 18-yard TD pass to Darrius Shepherd with 35 seconds left, the Bison defense was trampled by the Panthers for 277 yards on 38 carries. It was the most rushing yardage yielded by North Dakota State since it gave up 287 in a 34-24 loss at Illinois State on Oct. 16, 2010.

The Bison had limited their first four opponents to 40.8 rushing yards per game before letting UNI run for a season-high 7.3 yards per carry. Quarterbacks Aaron Bailey and Sawyer Kollmorgen combined for 216 of those yards, and coach Chris Klieman's group will face a similar challenge this week in dual-threat Coyote quarterback Ryan Saeger.

"We've got to come up with a good plan, because he can beat you with his arm and he can beat you with his legs," Klieman said.

Illinois State aims for a fifth consecutive victory behind the legs of running back Marshaun Coprich, who has averaged 152.0 rushing yards per game during the winning streak. He's 131 shy of becoming the conference's 14th player with 4,000 for his career.