Michigan State linebacker Joe Bachie talks about Saturday's loss to Northwestern and the road ahead. The Detroit News


East Lansing — There has been plenty of focus on Michigan State’s offense this season, and for good reason. The running game continues to be a non-factor and the Spartans simply aren’t scoring points at a rate that will give them a chance to win most weeks.

But things haven’t been perfect on the defensive side of the ball, either.

Yes, the Spartans are dominant against the run and were so again Saturday, allowing just 8 yards against Northwestern. They also created a pair of turnovers that led to 10 points. But the big plays bit them again — a 77-yard touchdown pass was the first on Saturday — and the defense couldn’t contain the Northwestern passing attack as the Wildcats came away with a 29-19 victory.

“When you lose a football game, you look back at three, four, five plays that are difference makers and game-changers,” defensive coordinator Mike Tressel said. “I think that if you have 80 snaps of football and 70 of them are fantastic, that doesn't necessarily win you a football game. I don't have to tell you which plays I can look back on, whether they are penalties or big passes, whatever they might be.

“The critical ones, the critical ones at the end of a victory, you look back and say we got the critical ones accomplished. When you lose, you look back and say we didn't get it done in the critical moments.”

More: Davis a steady force in MSU's sputtering offense

More: Injuries take their toll in Michigan State's loss to Northwestern


MSU captain Khari Willis talks about the "little things" that need to be fixed after losing to Northwestern. The Detroit News

There were only a few misses for the MSU defense on Saturday, but they were certainly critical. The coverage bust on Kyric McGowan’s 77-yard score in the first quarter was chief among them but failing to get off the field at key times was as crucial.

The Spartans got off the hook when Northwestern missed a field goal in the fourth quarter after a 13-play drive, but that came after they allowed the Wildcats to march down the field and retake the lead in the third quarter on a 21-yard strike to Cameron Green. That drive was kept alive by an unsportsmanlike conduct penalty on defensive tackle Naquan Jones, who celebrated a big hit.

“I was shocked there was a penalty on that play,” Tressel said. “I thought Naquan Jones made a great play. I'm not involved in the decision beyond that. It's unfortunate. I love watching our guys make great plays, but obviously there is a line they can't cross.”

In the end, Michigan State allowed Northwestern quarterback Clayton Thorson to throw for 373 yards and three touchdowns as the Spartans entered the game 13th in the Big Ten in passing defense.

“Yeah, you know it's tough,” linebacker Joe Bachie said. “They were racking up yards by passing the ball a lot. We had trouble. We had a couple blown assignments which hurt us at the end. We'll watch film on Monday as a group, then we'll understand stuff like this adds up at the end of the game. We'll learn and improve.”

The Spartans haven’t dealt with injuries on defense like they have offense, but cornerback Josiah Scott hasn’t played this season while his replacement, Josh Butler, has been slowed the last two weeks.

So, while Michigan State doesn’t allow teams to run the ball, it has a long way to go against the pass.

“Pass efficiency defense is as important as anything if you crunch numbers right now,” Tressel said. “It is an area of focus, it will continue to get better. Our guys, myself, our staff, we're committed to making sure that pass defense, when people talk Michigan State down the road, no fly is what they are talking about.”

Twitter: @mattcharboneau