What's the matter with Michigan?

Don't get it twisted: Most of what happened in State College, Pa., on Wednesday night -- winless Big Ten doormat Penn State shocking No. 4-ranked Michigan, 84-78 -- happened thanks to Penn State.

Jermaine Marshall and D.J. Newbill made those crucial buckets in the final four minutes; Sasa Borovnjak made the key late free throws; the Nittany Lions defended Glenn Robinson III's final last-ditch misses. More than road misery and failure, Wednesday night's prevailing story is one of hard-earned triumph.

But the fun half of the story -- perseverance and unlikely triumph -- couldn't exist without the other, which is where we have to take a step back and pose a perfectly valid question: Just what is the matter with Michigan?

Because it's not just the loss at Penn State. Indeed, this isn't the first time in the past 10 days the Nittany Lions have pushed the Wolverines for 40 minutes. That came on Feb. 17, a Sunday, when Penn State led Michigan 18-11 at the 10-minute mark and played the Wolverines close for the rest of the game in Ann Arbor. The final score, 79-71, came on just 66 possessions.

There were signs for concern before that, too. After that thrilling Feb. 2 "College GameDay" special at Indiana, an 81-73 IU win, Michigan had to fend off Ohio State in overtime in its own building 76-74 in one of the often-stagnant Buckeyes offense's best performances. On Feb. 12, John Beilein's team was hammered at Michigan State, 75-52. (Sandwiched between those two games was a 65-62 loss at Wisconsin, which doesn't count because it came in overtime after Ben Brust hit a regulation-ending half-court shot. We can all forgive that one.)

Thanks to a 20-1 start through November, December and January, we anointed Michigan as one of the nation's select handful of national title contenders. And rightfully so. Then, as it suffered through its worst patch of Big Ten schedule, we overlooked the defects. Also rightfully so. At Indiana, vs. Ohio State, at Wisconsin, at Michigan State? Who wouldn't struggle against that?

But there are some issues here, and they're the ones we've always had to worry about with this Michigan team, coached as it is by Beilein. Those issues can essentially be summed into one word. That word is defense.

In the past seven games, Michigan has allowed 1.11 points per possession to its opposition. Remember, that includes two games against Penn State, the league's least efficient offense, one averaging just .89 points per trip in conference play before Wednesday. Before Wednesday, the Wolverines were averaging an even 1.00 points per trip against Big Ten competition -- good for sixth-best in the conference. They had allowed opponents to make 48.9 percent of their two-point field goals, the highest percentage in the Big Ten, and they had blocked the fewest percentage of available shots (just 7.7. percent) of any team in the conference, too. According to Ken Pomeroy's adjusted efficiency rankings, the Wolverines rank No. 42 in the country in defensive efficiency -- good, but not great, and hardly among the elite units in the country. (For a handy snapshot of this stuff, John Gasaway's Tuesday Truths should be on your list.)

The upshot of all of this is that while Michigan's offense has been chugging along, posting efficiency numbers akin to Indiana's and keeping Trey Burke very deservedly in the conversation for national player of the year, Michigan's defense has slowed considerably. Simply put, teams with league-average defenses -- even if that league average is the Big Ten -- don't win national titles.

This was always the biggest question about Michigan, more than if it could meld Burke and Tim Hardaway and all the young talent into something great. The question was whether or not Beilein, who has never coached a top-25 efficiency defense in his career, at least since 2003, could mix all of that offensive potency with a defense that could at least get stops. Indiana faced a similar challenge last offseason, a hyper-efficient offense with a returning freshman star and sights set on a national title. The Hoosiers, who rank third in the Big Ten in defense (and have the No. 1 offense in the country) have largely answered the bell.

Michigan's offense is that good. It will be in March, too. Its defense, on the other hand, appears to be trending in the opposite direction -- and at the worst possible time of the season.

So while the Nittany Lions celebrate their monumental win, and IU and Michigan State breathe a sigh of relief, and fellow No. 1 seeds across the country thank their lucky stars, the Wolverines have much more pressing concerns. If they want to get to the Final Four, they have to fix this defense before it's too late.