So, which team is your Big Ten front-runner entering the fourth week of league play?

Seriously, I'd like to know. Because right now, it appears to be a complete toss up.

Entering last week, four Big Ten basketball teams were inside the top 15 in both national polls. All four lost.

There are no more teams with unblemished conference records, and the top eight teams in the standings are separated by one and a half games.

Here are this week's rankings:

Driver's seat

Vacant

Ohio State lost. Michigan State lost. Indiana lost. Michigan lost. This thing is wide open, folks. And, we just got started.

Contenders

No. 9 Michigan State (15-3, 4-1)

Last week: W 95-61 vs. Iowa, L 81-74 at Northwestern

Up next: at No. 20 Michigan (today), vs. Purdue (Saturday)

Michigan State blasted Iowa by 34 points earlier in the week, running its winning streak to 15 games and looking as dominant as ever. Then Northwestern came calling. The Spartans struggled against Bill Carmody's Princeton-style offense, losing to the Wildcats for just the fourth time in the Tom Izzo era.

No. 6 Ohio State (16-3, 4-2)

Last week: L 79-74 at Illinois, W 80-63 vs. No. 8 Indiana

Up next: at Nebraska (Saturday)

The Buckeyes were stunned by a 43-point effort from Illinois' Brandon Paul earlier in the week, but rebounded in a major way against Indiana on Sunday. Ohio State looked like the team everyone believes it can be against the Hoosiers, holding Indiana to 14 first-half points and getting revenge for a road loss earlier this season.

No. 11 Indiana (15-3, 3-3)

Last week: L 77-74 vs. Minnesota, L 80-63 at No. 5 Ohio State

Up next: at Nebraska (Wednesday), vs. Penn State (Sunday)

This was Indiana's worst week of the season, and it's not close. The Hoosiers were just 4-for-18 from 3-point range against Minnesota, which hadn't won a Big Ten game prior to this week. And at Ohio State? A disaster. The Hoosiers struggled from deep again (33.3 percent), turned the ball over 16 times and allowed Ohio State to shoot 54.4 percent.

No. 20 Michigan (14-4, 4-2)

Last week: W 66-64 (OT) vs Northwestern, L 75-59 at Iowa

Up next: vs. No. 9 Michigan State (today), at Arkansas (Saturday)

Michigan did exit last week with a victory, but was close to dropping both games. The Wolverines were 15-for-61 from 3-point range against Northwestern and Iowa, and shot just 37.6 percent from the floor in both games. Michigan got nothing from Tim Hardaway Jr. and Evan Smotrycz at Iowa, and remains winless on the road.

No. 22 Illinois (15-3, 4-1)

Last week: W 79-74 vs. No. 5 Ohio State

Up next: at Penn State (Wednesday), vs. Wisconsin (Sunday)

Illinois had just one game last week, and it was the team's biggest victory of the season. Thanks to Brandon Paul's 43 points, the Illini push themselves back into the contender group — for now, anyway. But, can Bruce Weber's squad remain consistent? That'll be the key.

On the fringe

Wisconsin (14-5, 3-3)

Last week: W 67-62 at Purdue, W 50-45 vs. Nebraska

Up next: vs. Northwestern (Wednesday), at No. 22 Illinois (Sunday)

Wisconsin was in a bad, bad place a week ago, but Bo Ryan is too good of a coach to let the funk continue. The Badgers found life for the first time this month with a victory at Purdue and another at home against Nebraska. Those aren't signature victories, by any stretch. But they may be enough to wake this bunch up.

Northwestern (12-5, 2-3)

Last week: L 66-64 (OT) at No. 13 Michigan, W 81-74 vs. No. 6 Michigan State

Up next: at Wisconsin (Wednesday), at Minnesota (Sunday)

Northwestern outplayed Michigan for the better part of 30 minutes on Wednesday, but was unable to close in regulation and ran out of steam in overtime. The Wildcats had no such problem against Michigan State on Saturday, though, earning a major feather-in-the-cap victory that could go a long way come bubble time in March.

Purdue (13-5, 3-2)

Last week: L 67-62 vs. Wisconsin

Up next: vs. Iowa (today), at Michigan State (Saturday)

I'm not ready to drop Purdue into the "outside looking in" category yet, but the Boilermakers are in need of a consistent stretch to turn me into a believer. Purdue has talent and Matt Painter can coach, but the team is toward the bottom of the league in field goal percentage (44.6) and 10th in the league in rebounding margin (+0.1).

Outside looking in

Iowa (11-8, 3-3)

Last week: L 95-61 at No. 6 Michigan State, W 75-59 vs. No. 13 Michigan

Up next: at Purdue (today)

Would the real Iowa basketball team please step forward? The Hawkeyes were embarrassed by more than 30 points in losses against Ohio State and Michigan State, but responded with a 75-59 win at home against Michigan. Iowa's learning plenty of difficult lessons this season under Fran McCaffery, but should continue to improve moving forward.

Minnesota (14-5, 2-4)

Last week: W 77-74 at No. 8 Indiana, W 80-66 at Penn State

Up next: vs. Northwestern (Sunday)

Break up the Gophers. After dropping its first four league games, Minnesota stunned Indiana on its home court before ripping Penn State for a second-straight road win. The Gophers are a flawed basketball team, but at least there's some confidence brewing.

Nebraska (9-8, 1-5)

Last week: W 70-58 vs. Penn State, L 50-45 at Wisconsin

Up next: at No. 11 Indiana (Wednesday), vs. No. 6 Ohio State (Saturday)

Nebraska made school history last week by beating Penn State, grabbing the program's first Big Ten basketball victory. Then, the Cornhuskers were held to 45 points in a loss at Wisconsin. It might just be that kind of year in Lincoln.

Penn State (9-10, 1-5)

Last week: L 70-58 at Nebraska, L 80-66 vs. Minnesota

Up next: vs. No. 22 Illinois (Thursday), at No. 11 Indiana (Sunday)

The only Big Ten team with a losing record, Penn State had an ugly week against current league bottom-feeders Nebraska and Minnesota. And if the team's 38.8 field goal percentage doesn't improve, Nittany Lions aren't likely to get back above .500.

Nick Baumgardner covers Michigan basketball for AnnArbor.com. He can be reached at 734-623-2514, by email at nickbaumgardner@annarbor.com and followed on Twitter @nickbaumgardner.

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