The mind never stops whirring, the fingers never stop tapping. John Beilein is in the backseat of a car, being driven through the countryside on a recruiting trip. He is talking on the phone, and he is watching game tapes on his computer.

“I don’t have a lot of time,” he says, politely. “Every minute is a minute I don’t get to prep for this game.”

Beilein is forever driven, even while being driven. When he arrived at Michigan in 2007, there was no real foundation, no real expectation and certainly no competitive Michigan-Michigan State basketball rivalry. At the time, Tom Izzo had won 18 of the previous 21 meetings. While Izzo also focused on Big Ten titles and Final Fours, he never took his eyes off his rival.

It took Beilein a little while to grasp the enormity of the job. It has taken the past few seasons to grasp the enormity of the rivalry, which has grown from big to bigger to the biggest clash yet, Saturday night in the Breslin Center.

“It took us three years to get our program to the level where we could compete with them, three long, hard years of building culture,” Beilein said. “These games are such incredible atmospheres. I see that it means more and more to our fans now, so it means more and more to me.”

The passion deficit between the fan bases has shrunk as Michigan has risen. If Beilein wasn’t sure at first, he knows now how much the rivalry matters. The No. 9 Spartans (23-6) and No. 7 Wolverines (26-4) will play for a share of the Big Ten title, and if Purdue, also 15-4 in the conference, loses at Northwestern, our Mitten Madness will decide the outright champion.

Coincidentally, Duke and North Carolina meet earlier Saturday night for a shot at the ACC crown, although Virginia is in control. In one mildly exaggerated sense, Duke-North Carolina is the JV matchup, a nostalgic appetizer before the big boys clash. OK, not really. The Tobacco Road rivalry stretches across 50 years and nine miles from campus to campus. Mitten Madness stretches across about a decade.

“My hope is that in the future, because of the great alumni bases of Michigan and Michigan State, this game will continue to grow,” Beilein said. “Duke-North Carolina is maybe a sexier rivalry. We might not have the megastars from all over the country, but this one’s pretty darn good too.”

No retreat under Izzo

Izzo’s program certainly hasn’t retreated in his 24 seasons, and his rivalry fire still burns hot, evidenced by the wild locker room celebration after the Spartans’ 77-70 victory two weeks ago. The surprise element is the tremendous success of Beilein’s program, with two national-championship appearances since 2013. In 12 seasons, he’s 9-12 against the Spartans, and since 2011, when the Wolverines finally busted through with a 61-57 victory in East Lansing, he’s 9-8.

Michigan had won three in a row before the Spartans showed up in Ann Arbor and conducted a flawless clinic, led by Cassius Winston.

Izzo and his staff strategized expertly in that one, switching their ball-screen defensive tendencies, teasing the Wolverines into ill-advised 3-pointers (seven-for-26).

Winston outdueled Zavier Simpson with one of the great point-guard performances Beilein said he’d ever witnessed, with 27 points and eight assists.

The theory is, Izzo adjusted and it’s Beilein’s turn to counter. There’s another possible matchup in the Big Ten tournament, then another possible NCAA Tournament run. But right now, there’s only a lonely road and a computer screen.

“The first game? Well, you always learn from every game,” said Beilein, 66. “I’m just absolutely amazed after 41 years, some 1,300 games, every day there’s something in basketball where I say, man, I never thought of that in my life. It’s like this incredible math problem that never stops, the angles and the physics of basketball that you continue to examine and change.

"And then somebody counters it, and then you gotta counter the next one.”

For a moment, he sounds distracted, talking in a clipped cadence. This is what Beilein does best, tackling tactical issues deliberately, constantly, with a mind acknowledged as one of the sharpest in basketball.

“It’s hard,” he says. “It’s a Rubik’s Cube, and there’s only one way to solve it.”

A constant puzzle to solve

It’s a different Rubik’s Cube every game, every season. When opponents began adjusting to Michigan’s 3-point-heavy offense, or simply tried to outscore the Wolverines, Beilein wasn’t stubborn. He adjusted with a ramped-up emphasis on defense and hired an assistant specialist in Luke Yaklich. Now the Wolverines are as tough defensively as any team in the country.

They might be without one of their top defenders Saturday night, with Charles Matthews nursing an ankle injury.

Of course, the Spartans have played without two of their best players — Nick Ward and Joshua Langford — which has allowed (even forced) Winston to flourish in every way. If he doesn’t wear down from the workload, you get the sense he can lead his team anywhere.

Both teams lost key players from last year’s squads, yet here they are again, scrapping for titles, led by superior coaches. The Spartans under Izzo, 64, generally know who they are and what they’re about.

They defend, they rebound, they contend. Although they’ve exited the NCAA Tournament early three years in a row, they’re in position to win their second straight Big Ten regular-season title.

The Wolverines under Beilein more regularly have to redefine themselves, as so many players develop rapidly and leave for the NBA. Heck, Beilein considered it himself last summer when he interviewed with the Pistons. Yet the Wolverines have won back-to-back Big Ten tournament titles and played in the NCAA championship game last season, and this team could be just as dangerous if shooters Jordan Poole and Ignas Brazdeikis get hot.

Beilein calls setbacks “pruning,” from his days on the family’s apple farm. You have to cut back and lose some pieces so new ones can grow.

Since the loss to Michigan State, you can bet he’s done some pruning. Winston tore apart Michigan’s vaunted ball-screen defense, although Simpson didn’t play poorly. Seven-footer Jon Teske has developed into a fine at-the-rim defender and leads the Big Ten in blocked shots, but had only one in the first meeting.

Izzo and the Spartans adjusted, which doesn’t mean they won’t adjust again, and doesn’t mean Michigan will make radical changes.

“I just don’t think it matters in this rivalry, especially with all we’re playing for,” Izzo said. “I think Michigan feels they can beat us and we feel we can beat them.

“The first game was close, so the last five minutes went our way. I don’t think that means they’re gonna be afraid to come in here, and I don’t think that means we’re gonna be cocky thinking we got this thing sewed up.”

Anxious until tip-off

Back on the road, Beilein is anxious to move onto the next thing. He says he’ll be anxious right up until the 8 p.m. tipoff, wondering if he watched enough tape and considered enough strategy. In that sense, he’s no different than a lot of coaches, no different than Izzo.

Beilein displays his emotions differently, rarely raising his voice, rarely criticizing. That should never be mistaken for reduced passion.

“I think there was a lot of emotion when we lost to them,” Beilein said.

“Hopefully we learned a lot from that experience. You play with emotion, you don’t play emotional, right? It’s great. I know I’m gonna embrace it, Tom probably will too. The Big Ten schedule couldn’t have worked out any better. Hopefully, every year we’re playing each other the last game, and this could repeat itself.”

There’s never been a matchup like this in our state, not with these stakes, not with the national glare. After years of wondering if a rabid basketball rivalry ever was possible, it’s fully here. Even better, it should be here for a while.

Twitter: @bobwojnowski