The top half of the Power Rankings remains exactly the same, but some interesting story lines are starting to develop.

Is Ohio State or Michigan the Big Ten's best team? Michigan made its case Saturday night against Notre Dame, while Ohio State's bigger tests await in Weeks 5 and 6 (Wisconsin and Northwestern). For now, we're keeping the Buckeyes at No. 1, but we'll need to see a strong performance this week on the road against Cal's high-powered offense.

Northwestern and Wisconsin held steady, and both Nebraska and Penn State looked better in Week 2. Illinois is the big mover after Saturday's dominant win against Cincinnati, while Indiana, Michigan State and Iowa fall. There's some separation after the top six, and Nos. 7-9 really could appear in any order.

These are consistent with our rankings in the ESPN.com power poll.

Here's one last look at the previous Big Ten rankings.

To the rundown …

1. Ohio State (2-0, last week: 1): Braxton Miller's knee injury created some tense moments in Columbus, but Ohio State fans settled down and settled in to the smooth sounds of Kenny G (Guiton, that is). One of the nation's best backup quarterbacks torched San Diego State for three touchdowns as a Buckeyes team that sleepwalked through the second half in Week 1 took charge from the get-go. Ohio State's young defense will be tested much more this week by the "Bear Raid" offense at Cal.

2. Michigan (2-0, last week: 2): Debate the Notre Dame-Michigan rivalry all you want, but it mattered a lot for quarterback Devin Gardner and the Wolverines. Gardner proved he's a big-game quarterback and triggered an impressive offensive performance against Notre Dame's physical defense. Although Michigan's defense had some issues, it made timely plays against the Irish. The Wolverines have the look of a BCS bowl team and possibly a Big Ten champion.

3. Northwestern (2-0, last week: 3): Week 1 was all about survival for Northwestern. Saturday night, the Wildcats showed why they should contend for the Legends Division title this season. Quarterbacks Kain Colter and Trevor Siemian had their way with Syracuse's defense, and wideout Tony Jones had a huge night as Northwestern easily improved to 2-0. The Wildcats should be 4-0 in three weeks when Ohio State visits Evanston, and star running back Venric Mark should be healthy by then.

4. Wisconsin (2-0, last week: 4): The run game has been dominant, the defense suffocating and the competition level horrendous. What do we make of these Badgers after two not surprisingly dominant performances against lowly Massachusetts and Tennessee Tech? Wisconsin deserves credit for handling its business with few if any mistakes, recording back-to-back shutouts to open a season for the first time since 1958. Quarterback Joel Stave looks comfortable. But the competition goes up -- way, way up -- this week at Arizona State.

5. Nebraska (2-0, last week: 5): The Huskers defense doesn't deserve the "Blackshirts" label quite yet, but at least the unit avoided less-flattering terms for a week. Cornerbacks Stanley Jean-Baptiste and Ciante Evans set the tone for a rebound performance with pick-sixes in the first quarter, and junior-college transfer Randy Gregory applied pressure all game. The defense needs a better performance this week against UCLA, potentially the only team that can beat the Huskers during the first two months of the season.

6. Penn State (2-0, last week: 6): After a rough start, freshman quarterback Christian Hackenberg settled down in his Beaver Stadium debut. He also got a ton of help from the run game, which had struggled in the opener but broke out for 251 yards and five touchdowns. Tackle DaQuan Jones triggered a suffocating Lions defense, which will be tested much more this week when Blake Bortles and Central Florida visit Happy Valley.

7. Minnesota (2-0, last week: 8): Although Aggie Vision was the real highlight Saturday night, Minnesota provided a few of its own in an easy win against New Mexico State. The Gophers continue to find creative ways to score, adding a special teams touchdown and a defensive touchdown in a 44-21 romp. Despite being short-handed at running back, Minnesota got the ground game going behind Rodrick Williams (148 yards, 1 TD), David Cobb (56 yards, 1 TD) and quarterback Philip Nelson (122 rush yards, 1 TD). The Gophers have another tuneup this week before their first real test Sept. 21 against San Jose State.

8. Michigan State (2-0, last week: 7): Can Shilique Calhoun play quarterback? The sophomore defensive end has been Michigan State's best offensive weapon in the first two games, scoring one more touchdown than the entire Spartans offense. Michigan State's defense has added a dynamic playmaking element early this season. Unfortunately, the problems on offense only seem to be worsening and the quarterback situation is anyone's guess right now.

9. Illinois (2-0, last week: 11): Surprise, surprise, the Illini are unquestionably on the rise. Few saw it coming, but Illinois walloped Cincinnati behind another impressive performance by quarterback Nathan Scheelhaase and the offense. One of the nation's worst offenses has surged under coordinator Bill Cubit, scoring 87 points in the first two games. Linebacker Mason Monheim and the defense rebounded nicely after a shaky Week 1 effort. Can the Illini pull off another upset this week against Washington at Chicago's Soldier Field?

10. Indiana (1-1, last week: 9): Kevin Wilson's words last week proved prophetic as Indiana's offense lacked the efficiency it needed early on against Navy's ball-control offense. But eventually a defense has to make some stops and Indiana's once again couldn't, especially in the closing minutes. The Hoosiers surrendered 444 rush yards in a 41-35 loss, once again showing that this program hasn't turned a corner. Things get tougher this week as a very good Bowling Green squad comes to Memorial Stadium.

11. Iowa (1-1, last week: 10): Some Iowa fans undoubtedly felt better about their team after last week's loss to Northern Illinois than Saturday's win against FCS Missouri State. The Hawkeyes had just seven points through the first 37 minutes before Mark Weisman (180 rush yards, 2 TDs) took over down the stretch. Quarterback Jake Rudock showed good mobility but also threw a pick-six. Iowa faces a must-win this week as it hits the road to face rival Iowa State.

12. Purdue (1-1, last week: 12): The Boilers got a win Saturday, but they won't win many more if they don't clean up their problems on offense. If Purdue can't punch the ball into the end zone against Indiana State from inside the 5-yard line, what's going to happen against Big Ten defenses? Defensive tackle Bruce Gaston had a big day, but the Boilers need many others to elevate their play as Notre Dame visits Ross-Ade Stadium this week.