It's no secret Michigan's defense hasn't been good this season even by the generally mediocre standard set by previous John Beilein teams. The Wolverines rank 134th nationally in defensive efficiency on KenPom; if that stands, it would be the lowest mark in Beilein's tenure by a healthy margin.
When I first watched the Iowa game, I hoped to find one or two issues I could isolate as the main cause of Michigan's defensive problems. On the first viewing, I identified a couple: Michigan's guards gave up the baseline too often, straining their already sub-par weakside defense. This example came to mind:
This was even worse:
There are two big problems on that play. Walton does a poor job defending the high side screen, allowing his man to turn down the pick and get the baseline. This forces Duncan Robinson to rotate over, which he does—he's improved a lot in that regard—but communication is lacking on the weak side and MAAR isn't in position to contest the corner three.
As the screencap at the top of the post indicates, communication was the other deficiency I noticed right away. When Michigan doubled in the post or switched on a screen, they often ended up with two players guarding one guy off the ball while the other was left alone for a layup. Screencaps are sufficient here; both these plays ended in a layup:
Jarrod Uthoff got a crucial late bucket when Iowa ran a pair of baseline screens and Aubrey Dawkins had no idea who to guard:
Those two issues—dribble penetration opening up weakside threes and blowing rotations off the ball—caught my attention on the first viewing.
Unfortunately, a second pass through the game revealed more problems. A couple Iowa three-pointers I initially believed were caused by the weakside defender were instead the product of poor pick-and-roll defense. Michigan eschewed their normal hard hedge against high screens in favor of a softer, more conservative approach for much of the game, and they didn't execute it well.
On this play, Dawkins gets hung up on the screen too long, which causes a domino effect—Mark Donnal has to wait an extra beat before sinking back into the paint, which forces MAAR to stay on the rolling big instead of getting back to his man in the corner:
On this pick-and-roll, Iowa gets a layup when Walton and Donnal play soft, Mike Gesell has an open passing lane, and the help from Robinson is late and wouldn't have prevented an Adam Woodbury bucket regardless:
One more P&R failure for good measure: when Michigan went back to a hard hedge, Walton doubled Uthoff in the paint instead of guarding Woodbury, who was all alone next to the basket.
Finally, Michigan also had trouble identifying shooters in transition, something Beilein discussed in the postgame presser. On this play, Iowa pushes the pace off a defensive rebound, and the Wolverines initially stymie the attempt to get an easy bucket. Again, a lack of communication comes to the forefront, as Dawkins switches men while Iowa swings the ball around the perimeter, which is news to Donnal:
This is pretty basic stuff that Michigan still can't get right. A couple takeaways from the above:
There's no single fix. There's plenty of stuff that's gone wrong here that doesn't even touch on the lack of a true post presence, which I still believe is the biggest problem with Beilein's defenses. There isn't one defender at the heart of these issues—though Dawkins stands out in a bad way, this goes far beyond him. Getting this defense up to simply mediocre will require fixing multiple areas of deficiency.
But if I had to pick one, it's communication. A lot of these easy baskets result from players not talking to each other. Those screencaps are frustrating and telling.
Long story short, it's tough to see Michigan improving to the point where the defense isn't a liability. We're beyond the midway point and there are myriad problem areas. Players like Robinson and Donnal have progressed during the season from starting points that were frankly bad, but they may have maxed out their defensive potential for this season. Hopefully getting Caris LeVert back—whenever that may be—solves some of the communication problems, but those are also widespread enough that I doubt one man clears them up.
The good news is the offense has plenty of firepower. Michigan is going to have to lean on that for the duration unless they have a team-wide defensive improvement we haven't seen out of a Beilein team during the course of a single season.