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Five lessons from four games in Week 5. Got that?

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1. Ohio State's young defense is growing up: Lost amid the Braxton Miller-Kenny Guiton debate this week was the fact a mostly young Ohio State defense with only one returning starter in the front seven would be put to the test by Melvin Gordon, James White and the formidable Wisconsin run game. The young Bucks certainly earned a passing grade after holding Wisconsin to just 104 yards on 27 carries. Gordon's knee injury limited the Badgers, but Ohio State prevented big runs and forced Wisconsin to win the game through the air. Linebacker Ryan Shazier shined, while linebacker Curtis Grant and lineman Michael Bennett both recorded sacks. The loss of safety Christian Bryant to a season-ending ankle injury is a big blow, but Ohio State has enough talent in the secondary to make up for it, as long as they don't run into Jared Abbrederis again soon. Ohio State's offense will win plenty of games, but you know what they say about defenses and championship. These might not be the typical Silver Bullets, but they're developing and can build on Saturday's performance as they face an even another formidable offense in Northwestern next week.

2. Wisconsin is an excellent 56-minute team: Gary Andersen's crew showed plenty of grit Saturday night in Columbus. Quarterback Joel Stave quieted some of his critics -- thanks in large part to a career performance from Abbrederis (10 catches, 207 yards, 1 TD) -- and linebacker Chris Borland was brilliant, as usual. But Wisconsin's inability to finish off halves remains a troubling trend, and it surfaced in the loss to Ohio State. The Badgers trailed by only three points when freshman cornerback Sojourn Shelton dropped an easy interception near the goal line. Miller found Philly Brown for a 40-yard touchdown on the next play, giving Ohio State a huge boost with one second left in the half. Wisconsin struggled to manage the clock down the stretch as its comeback attempt fell short. This isn't a team built to come back in games based on the pass game, and it showed. Coupled with the Arizona State debacle (granted, more officiating than execution), Wisconsin has had a lot of bad things happen at critical moments. That's what could separate the Badgers from a fourth consecutive Big Ten title.

3. Iowa will be a factor in the Legends Division: The Hawkeyes might not be a great team yet, but it's clear they are vastly improved from last season. On Saturday, Iowa went into Minnesota and pushed the Gophers around on their home turf, piling up 464 total yards and allowing only 30 rushing yards in a 23-7 win. The pig will return to Iowa City, but even more importantly, the hogs up front are getting it done in classic Kirk Ferentz fashion. Iowa has rushed for at least 200 yards in every game this season and went for 246 against a Minnesota defense that thought it had made strides in that area. This team has an identity, and it starts with the power running game led by Mark Weisman and a solid offensive line. Quarterback Jake Rudock has shown an ability to extend plays, and Iowa even got an explosive play in the passing game when Damond Powell took a short pass 74 yards to paydirt. The defense is also playing well right now; the Gophers' only score came after a long kickoff return. The Hawkeyes are 4-1 and gets Michigan State at home next week, while Northwestern and Michigan still must come to Kinnick Stadium. The schedule is difficult the rest of the way, but Iowa will have a big say in who wins the Legends.

4. Nathan Scheelhaase is the Big Ten's most improved player: A year ago, Scheelhaase was sputtering at the helm of one of the nation's worst offenses, hardly resembling the player who had shown promise as a freshman and during the first part of his sophomore season. No Big Ten player has made bigger strides in the past season than the Illinois senior quarterback, who threw five first-half touchdown passes Saturday against Miami (Ohio) and finished with 278 pass yards on 19 of 24 attempts. Scheelhaase leads the Big Ten in passing yards and is second in touchdowns (12), tripling his total from last season. He's just five touchdown passes shy of his single-season best and 15 shy of Kurt Kittner's single-season team record. Offensive coordinator Bill Cubit deserves a lot of credit for Scheelhaase's surge -- and that of the entire Illini offense -- but Scheelhaase clearly is back on track after a year and a half in the dark. It will be interesting to see what he does this week against Nebraska's shaky defense.

5. Future starts now for Etling, Purdue: Darrell Hazell stuck with senior quarterback Rob Henry through this season's early offensive struggles, but the Purdue coach realized it was time for a change Saturday against Northern Illinois. The last straw was Henry's second interception of the first half, a terribly thrown floater into the Huskies' end zone. That prompted Hazell to give the reins over to true freshman Danny Etling, the prized former recruit who made his collegiate debut. This was no fairy tale, so Etling didn't lead the Boilermakers to a comeback victory. He threw two interceptions, including a pick-six, and narrowly avoided another one. But Etling (19-for-39, 241 yards) did show good mobility and flashed his strong arm, especially on his first career touchdown pass, a 16-yarder to Cameron Posey. The offense will have more of a chance to stretch the field with him under center. Quarterback is hardly the only problem for Purdue, which got housed 55-24 at home by a MAC team and might have a hard time finding another win this season. But while Boilers fans don't like to see the words "Danny" and "hope" in the same sentence, Etling at least gives them something to look forward to as Hazell tries to work the program out of this mess.

Good news: We are just 100 days away from the start of college football.

To mark the occasion, we're pulling out a checklist today of things that Big Ten teams need to accomplish between now and the start of the season. It's not quite "The Final Countdown" (cue GOB Bluth), but we are inching ever so close to kickoff. Here's what needs to happen in the next 100 days:

1. Identify a starting quarterback at Iowa, Indiana, Michigan State, Penn State, Purdue and Wisconsin: It seems as if there are an unusually high number of Big Ten teams who don't know for sure who their starting quarterbacks will be in the fall. (You could also add Illinois and Minnesota to this list, though it appears likely that Nathan Scheelhaase and Philip Nelson, respectively, would have to lose the job in the summer.) Iowa had a three-man race this spring that will probably come down to Jake Rudock and Cody Sokol in training camp. There's very little separation between Cameron Coffman, Nate Sudfeld and Tre Roberson at Indiana. Connor Cook continues to breathe down the neck of incumbent Andrew Maxwell at Michigan State. Tyler Ferguson claimed the starting job at Penn State during the spring, prompting Steven Bench to transfer, but highly touted recruit Christian Hackenberg will push for immediate time. Purdue will likely decide between senior Rob Henry and true freshman Danny Etling. Joel Stave and Curt Phillips separated themselves from the Wisconsin QB derby this spring, while incoming junior college transfer Tanner McEvoy could expand the race this summer. All these situations should work themselves out in August, but no team wants to be dealing with an unsettled quarterback competition once the season starts.

2. Solidify the defensive front sevens at Nebraska and Ohio State: The Huskers and Buckeyes stand out as two of the top Big Ten contenders in 2013, but both have serious questions at defensive line and linebacker. The issue is more dire at Nebraska, which struggled there last year and is replacing all but one starter from 2012. Summer arrivals, including junior college star Randy Gregory, could make an immediate impact, and players coming back from injury such as linebacker Zaire Anderson and defensive tackle Thad Randle will need to play up to potential. Ohio State is less concerned about its defense after the spring performance of defensive ends Noah Spence and Adolphus Washington, but linebacker Ryan Shazier is still the only returning starter in the front seven. Curtis Grant must finally live up to his talent to provide help to Shazier, and someone must assume John Simon's leadership role.

3. Locate the next great receivers: A few Big Ten teams, such as Nebraska, Penn State and Indiana, don't have to worry too much about who will catch the ball this year. But just about everybody else needs to find playmakers in the passing game. The top of that list includes Iowa, which couldn't generate a downfield passing attack last year; Illinois, which needs receivers to make new coordinator Bill Cubit's spread system work; Michigan State, whose young wideouts must improve on last year's shaky performance; Minnesota, which doesn't have many proven weapons to surround Nelson; and Wisconsin, which still must find a complement to Jared Abbrederis. Ohio State coach Urban Meyer is hoping some incoming freshmen augment a very thin receiver group, while Michigan needs to replace the production of Junior Hemingway and Roy Roundtree. Purdue and Northwestern have lots of speedy options but could use the emergence of a true No. 1 target. Receiver was a weak spot as a whole in the Big Ten in 2012, and hopefully some players will improve through offseason voluntary passing drills.

4. Strengthen the running game at Michigan, Michigan State, Indiana and elsewhere: It's a cliché to say that you have to run the ball to win, but in the case of the Big Ten, that's always been true. That's why it's so vital for the Wolverines and Spartans -- who both expect to contend in the Legends Division -- to find answers in their rushing attacks. Michigan is replacing its entire starting interior offensive line after struggling to get a running game going outside of Denard Robinson last year. Fitz Toussaint is hoping to bounce back from a disappointing season and a leg injury, while hotshot freshman Derrick Green could get lots of carries right away. Michigan State's efforts to replace workhorse extraordinaire Le'Veon Bell this spring ended up with converted linebacker Riley Bullough emerging as the top back in a mediocre field. Three incoming freshmen will compete for time right away this summer. Indiana coach Kevin Wilson put a heavy emphasis on the running game this spring, hoping for more balance after his team led the league in passing and finished last in rushing last season. Iowa has depth for once at running back but needs to stay healthy there, as the ground game is the key to the Hawkeyes' entire offensive philosophy. Nebraska also can't afford injuries, as Ameer Abdullah and Imani Cross are the lone backs with any experience. Illinois averaged just 3.5 yards per carry as a team last year, a number that must improve. And while Purdue loved what it saw from Akeem Hunt this spring, he still must prove he can be an every-down back after attempting only 42 carries last season.

5. Mesh with new coaches: Wisconsin's Gary Andersen and Purdue's Darrell Hazell are the fresh faces among head coaches in the league, and while they did a great job of connecting with their players this spring, they still need to get their new systems fully in place. The Badgers will be using some new, 3-4 looks on defense, while Hazell wants a more physical and disciplined team than we've seen from the Boilermakers of late. Michigan State has a new offensive playcaller in Dave Warner, while Cubit was one of many staff changes at Illinois. Penn State's John Butler takes over from Ted Roof as the Lions' defensive coordinator. With only 15 spring practices so far to implement their styles, those new coaches have had to rely on a lot of classroom time and players learning on their own. That will have to continue this summer during voluntary workouts and then will intensify when preseason practice begins. For new coaches, it's a race against the calendar -- and the calendar says there are only 100 days until kickoff.