Big Ten power rankings: Week 4

Posted by ESPN.com's Adam Rittenberg

Ohio State answered the bell and finally dominated a team, while the Big Ten's upper crust has separated itself. The top five look pretty solid, while the bottom six are a muddled mess.

1. Penn State (3-0) -- The exhibition season is over for Penn State, which looked better on offense and just as stingy against Temple. The Lions finally established a decent running game, and not a moment too soon with Iowa visiting Happy Valley this week. Linebacker Sean Lee has been fabulous in his return to the field, and Penn State's defense is setting the tone. But things are about to get much tougher.

2. Ohio State (2-1) -- I probably punished the Buckeyes a little too much last week, but I needed to see them deliver a convincing performance against an inferior opponent. Terrelle Pryor and the much-maligned offense clicked against Toledo, and the defensive line was merciless against Aaron Opelt and the Rockets. The Buckeyes defense has things rolling right now as Juice Williams returns to Columbus this week.

3. Michigan (3-0) -- This has more to do with Ohio State's overdue performance than anything Michigan did against Eastern Michigan. Wolverines freshman quarterback Tate Forcier looked his age at times Saturday, but Carlos Brown and the rushing attack picked him up nicely. A young Michigan defense still has some things to shore up against the run as it opens Big Ten play against Indiana.

4. Iowa (3-0) -- No Big Ten team has looked more impressive the last two weeks than the Hawkeyes, though national respect is still hard to come by. The good news? Iowa can gain a ton of cred by upsetting No. 5 Penn State on Saturday night in the Whiteout at Beaver Stadium. The defense must maintain its edge and quarterback Ricky Stanzi needs to limit his first-half mistakes in Happy Valley.

5. Wisconsin (3-0) -- The Badgers took care of business against FCS Wofford and continued to get steady play from junior quarterback Scott Tolzien. The schedule really favors Wisconsin this year, with four consecutive home games to begin the season, and Bret Bielema's team has capitalized. Michigan State will be a desperate team Saturday, but Wisconsin gets the Spartans and Camp Randall Stadium.

6. Minnesota (2-1) -- After a rough start, Minnesota rallied against Cal and made the nation's eighth-ranked team work for a victory at TCF Bank Stadium. Kevin Cosgrove and Ron Lee have the defense playing extremely hard, especially in the front seven. Eric Decker is a stud, but the offense remains far too one-dimensional. The Gophers will struggle in the Big Ten if they can't run the ball.

7. Indiana (3-0) -- Surprised to see the Hoosiers here? Well, they deserve it after their second 3-0 start in the last three seasons. Akron clearly missed suspended quarterback Chris Jacquemain, but Indiana took advantage of the situation and intercepted backup Matt Rodgers four times. The competition gets much harder this week at Michigan, but kudos to Bill Lynch and Indiana for the hot start.

T-8. Northwestern (2-1) -- The Wildcats resume looks pretty weak right now, with a blowout win against Towson and a close call against Eastern Michigan followed by a loss at Syracuse. A banged-up defense let Greg Paulus and Mike Williams pile up yards and points Saturday, leading some to believe that last year's improvement was a fluke. Quarterback Mike Kafka's play was very encouraging, but if the defense reverts to pre-2008 form, Northwestern will struggle in the Big Ten.

T-8. Michigan State (1-2) -- Credit the Spartans for playing extremely hard in South Bend, but they still came out with a tough loss. Listening to quarterback Kirk Cousins, who handled a difficult situation well, you'd think these Spartans won't go the way of their predecessors. A trip to Madison this week has to be classified as a must win before arch-rival Michigan visits East Lansing on Oct. 3.

10. Illinois (1-1) -- The Illini didn't play on Saturday, but they lost a huge piece of their defense last week as middle linebacker Martez Wilson (neck) will miss the rest of the season. Wilson will be missed, and linebackers Ian Thomas and Russell Ellington must pick up the slack. The biggest boost must come from Juice Williams, Arrelious Benn and the offense. Illinois season could be decided in the next three games (Ohio State, Penn State, Michigan State).

11. Purdue (1-2) -- A home loss to Northern Illinois carries a price, even though the Huskies are an improved team. NIU loaded up against the run and held Ralph Bolden in check, and Purdue couldn't get its downfield passing game going. It's hard to know what to make of Purdue, which should have beaten Oregon on the road but really struggled against NIU. The Boilers can strike back this Saturday night against Notre Dame (ESPN, 8 p.m. ET).