Saturday’s Wisconsin-Michigan is a huge part of the Big Ten race. Here’s how it’ll define things.

The last time Michigan played Wisconsin, Bret Bielema’s Badgers ran all over the defense of coordinator Greg Robinson. Montee Ball and James White combined for 354 yards and six touchdowns, Scott Tolzien threw for 201 yards, and No. 6 Wisconsin romped to a 48-28 win over 7-4 Michigan.

It’s been a while, in other words. Nearly six years have passed since the Badgers and Wolverines met, and under normal circumstances, that alone would make Saturday’s meeting at the Big House a well-anticipated event.

But there’s nothing normal here. Both are ranked in the top 10, and two different Big Ten division races could hinge on the result.

Each week at Football Study Hall, I post team statistical profiles that feature updated S&P+ win probabilities, Five Factors box scores, etc. The win probabilities tell us pretty interesting things about both division races.

Big Ten East projections

Our eyes were already telling us that it is a two-team race in the East. As impressive as Michigan State looked in beating a Notre Dame that hadn’t yet lost to Duke, the Spartans were uninspiring in a win over Furman and out of answers in a 30-6 loss to Wisconsin last week. They were woefully inefficient on offense, and it took them a quarter or two to figure out a Badger offense now led by Alex Hornibrook.

With preseason projections now playing only about a 30 percent role in the S&P+ ratings, State’s ratings now have no safety net.

Sparty fell from 30th to 47th this week: 21st on defense, but 77th on offense.

We know how well Mark Dantonio’s team plays as an underdog, and getting both Michigan and Ohio State at home will give the Spartans an opportunity to play a role in the East race — even if they are not contenders. But any sort of rebound needs to begin immediately: S&P+ gives MSU only a 44 percent chance of beating Indiana on Saturday evening.

With Sparty down, this race is two-dimensional. Ohio State vs. Michigan, Michigan vs. Ohio State.

Not surprisingly, both teams — the top two in overall S&P+ — are projected to win each game between now and the big game in Columbus on Nov. 26. Only a few are projected to be particularly close.

• Michigan is currently given under 80 percent win probability in only two games: Wisconsin this Saturday (79 percent) and at Iowa on Nov. 12 (79 percent).
• Ohio State, meanwhile, is under 85 percent only once: at Wisconsin on Oct. 15 (74 percent).

S&P+ loved both of these teams at this time last year, too, but Michigan’s run defense faded drastically, thanks in part to injuries. If injuries don’t interject again, we might end up with the most important UM-OSU game since 2006, when two undefeated teams met in a BCS eliminator.

Big Ten West projections

Impressions can change quickly. A week ago, we were trying to determine the significance of Wisconsin’s labored win over Georgia State, a slog that required them to work deep into the fourth quarter before putting the Panthers away, 23-17.

Now, following a dominant performance in East Lansing, we’re wondering if anyone can touch the Badgers in the West race. Spoiler: Yes.

Heading into October, the S&P+ ratings split the West into two tiers.

Wisconsin (No. 16), Nebraska (No. 23), Iowa (No. 28), and Minnesota (No. 35) are separated by only about 5.6 adjusted points per game.

Illinois (No. 71), Northwestern (No. 73), and Purdue (No. 89) lag far behind.

We reflexively think of teams based on their last impressions. Wisconsin is now clearly the best team in the West, even though we were wondering about mediocrity just a week ago. While wins over LSU and Michigan State pushed the Badgers ahead of their West brethren, it’s only by so much. And they still have the toughest upcoming slate among contenders.

• Wisconsin: Plays both Michigan (road) and Ohio State (home), gets two of three other contenders at home.
• Nebraska: Plays Ohio State (road), gets two of three West contenders on the road.
• Iowa: Plays Michigan (home), gets two of three West contenders at home.
• Minnesota: Plays neither Michigan nor Ohio State, gets two of three West contenders on the road.

Of the four contenders, the two best have the toughest upcoming roads. That could make for a fascinating race.

Maybe the West will be decided by Nebraska’s trip to Wisconsin on Oct. 29. But don’t count out Iowa and Minnesota just yet.

Iowa hasn't played inspired football over the last couple of weeks, losing to North Dakota State and winning by only seven at Rutgers. But over four games, the Hawkeyes have demonstrated both major offensive potential (87 points against Miami-Ohio and Iowa State) and sturdy defense (13.5 points per game allowed). Plus, they get both Wisconsin and Nebraska at home and avoid Ohio State.

Minnesota has improved slightly each week. The Gophers had to work to get past Oregon State but pummeled Indiana State and outgained Colorado State by nearly 2 yards per play this past Saturday. A shakier-than-expected Minnesota defense allowed CSU to stay closer than they should have, but the offense is improving enough to make up the difference.

Backs Rodney Smith and Kobe McCrary are averaging 6 yards per carry and 164 rushing yards per game, and quarterback Mitch Leidner is completing 65 percent of his passes, mostly avoiding mistakes, and averaging 5.6 yards per (non-sack) carry himself.

I'm not going to try to convince you that either the Hawkeyes or Gophers are strong teams. But they might be good enough to take advantage of scheduling and make a division run, especially if Wisconsin falters.

If the Badgers take down Michigan on Saturday, however, maybe this isn’t a race at all.

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Week 5 Big Ten slate:

AP rankings listed below. All times ET.

• Northwestern at Iowa (12 p.m., ESPNU)
• Rutgers at No. 2 Ohio State (12 p.m., BTN)
• Purdue at Maryland (3:30 p.m., BTN)
• No. 8 Wisconsin at No. 4 Michigan (3:30 p.m., ABC)
• Illinois at No. 15 Nebraska (3:30 p.m., ESPN2)
• Minnesota at Penn State (3:30 p.m., BTN)
• No. 17 Michigan State at Indiana (8 p.m., BTN)