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As sophomore defenseman Steve Holtz skated out of the box after facing an ejection for hitting from behind, his head looked down at his skates. With Notre Dame on a five-on-three power play in the waning minutes of the second period, Michigan had to play down a man for the second night in a row.

And for the second night in a row, the Wolverines’ discipline left them out to dry.

The Wolverines’ mental mistakes stretched far outside of that second period slump. No. 1 Michigan struggled to keep its composure all game against the grinding presence of No. 14 Notre Dame.

Just four minutes into the game, sophomore forward Matty Beniers took a tripping call that cost the Wolverines the puck. The Irish earned an early power play that tested sophomore goaltender Erik Portillo, but they couldn’t capitalize. The penalty did, however, disrupt Michigan’s surging momentum as its forwards peppered the Irish’s goaltender Ryan Bischel with shots.

Those unforced penalties fell like rain in the second period, the first drops hitting the ice when junior forward Johnny Beecher took an unforced hooking call behind the net. After Holtz’s hit soon after, the Wolverines killed just 22 seconds before senior defenseman Nick Blankenburg took a coincidental minor for slashing Notre Dame’s Landon Slaggert in the leg after getting checked from behind. Michigan could only hope to tread water as penalties sent players to the penalty box in a raging current to end the period.

While those penalties put the Wolverines down, they came from facing a tough, physical forecheck like Notre Dame’s. While most of the plays weren’t outlandish, their timing forced them into a corner.

“The major, that’s the only penalty that really concerned me,” Michigan coach Mel Pearson said. “Especially when you’re already down a man, you gotta be careful.”

But discipline issues extended far past penalties — it also spread to the Wolverines’ positioning. After scoring two gritty goals in a three minute span, the Wolverines rested on their back foot. Before the public address announcer could call a goal from sophomore forward Thomas Bordeleau, the Irish slashed the two-goal lead in half after slipping a loose puck past an out-of-position Portillo.

By the end of the period, Michigan’s defense lay in shambles as Notre Dame drew even. Its skaters left Notre Dame’s attackers wide open on multiple goals. Despite outshooting the Irish 41-21, the Wolverines left holes in their defense that left the game up for grabs.

It didn’t help that penalties kept Michigan off center all game. Many of its errors came from a combination of turnovers, bad positioning by Portillo and missed assignments on defense. Lines also shuffled throughout the game as Pearson worked with a short bench. Those all combined to keep the Wolverines uncomfortable.

Still, Michigan’s aggression creates the room for its offense to explode. The Wolverines have to find a middle ground of standing up for themselves and avoiding mental errors. They couldn’t find that on Saturday.

“They just had a couple good bounces and they’re putting the puck on net and it was just working,” Bordeleau said. “We can’t get too hard on ourselves with that.”

That kind of performance can be expected for a young team, but Michigan’s players have been in tough skirmishes before. After posting rather complete weekends for most of this season, Saturday’s performance looked like film straight out of last season’s inconsistency — which included another sweep from the Irish.

Michigan’s discipline — both in penalties and defense — has to fall in check if it wants to beat tough teams. Bad bounces led to some Notre Dame chances, but the Wolverines’ failing discipline exacerbated their danger. For a team eyeing a championship, Michigan can’t afford those mental lapses.