Be it a defense that's beaten down or an offense that's giving up easy scores, Notre Dame is permitting points at historically bad levels.
A week after allowing 55 points against Arizona State, with two touchdowns coming off interceptions thrown by Everett Golson, the Irish surrendered 43 to a Northwestern a squad that had been held to two TDs in the previous 10 quarters.
"We can't give up 40 points. I don't care what the offense does," safety Austin Collinsworth said. "We can't give up 40 points."
The Irish (7-3) fell out of the rankings for the first time this season following the 43-40 overtime loss Saturday. It marked the first time Notre Dame has given up at least 43 or more points in back-to-back games and just the second time Notre Dame has given up 30 points or more for five straight games.
It also was the third time this season the Irish have given up 40 points or more, tying the season high set in 1956 and matched in 2004 and 2006.
The Irish still have games left against Louisville (7-3), which is averaging 31.6 points a game but will be without quarterback Will Gardner, and Southern California, which is averaging 35.2 points.
Coach Brian Kelly said Sunday he knew the young Irish defense would hit some tough spots.
"I expected us to be in a couple of shootouts this year where we would have to overcome offensively. I just didn't expect to have nine turnovers in the last two weeks because I thought our offense would be able to bail out our defense and that hasn't been the case."
Kelly said with two freshmen and four sophomores starting on defense, the Irish need each younger player to just get incrementally better to see improvement.
"We've just got to eliminate the mental mistakes on defense and that's the hard part with a bunch of young guys," he said.
He reiterated that losing leaders like Collinsworth, a team captain who has been limited by injuries, and linebacker Joe Schmidt, who sustained a season-ending ankle injury on Nov. 1, has hurt because the defense has struggled with communication.
It may be further hampered, too. Defensive lineman Sheldon Day, another captain, sustained a sprained knee against Northwestern and was undergoing an MRI on Sunday.
Kelly said Golson sustained a shoulder sprain but doesn't expect it to keep him out against Louisville.
The Irish made a change on defense Saturday by replacing sophomore safety Max Redfield with freshman Drue Tranquill, but Tranquill struggled at times. Kelly said he'd make more changes if he could.
"Max isn't the only guy. There are other guys in that similar boat. We just don't have any other answers at other positions," he said.
One of the biggest problems has been big plays. Northwestern didn't have a run of longer than 27 yards this season until facing the Fighting Irish. Justin Jackson gashed the Irish for a 44-yard run on the Wildcats' first possession and Treyvon Green ran up the middle for a 45-yard gain later in the quarter. Trevor Siemian added a 60-yard pass to Cameron Dickerson that was the longest reception for the Wildcats.
"Just too many explosive plays," linebacker Jaylon Smith said.
Smith blames Notre Dame's defensive troubles on lack of execution.
"Thinking too much. We don't have all 11 guys playing fast, playing careless and free and fast. That's something we have to assess and look ourselves in the mirror," he said. "You have to stop losing before you start winning. We're beating ourselves, and we really have to get better and keep executing."