Minnesota Vikings defensive end Danielle Hunter, left, closes in on Lions quarterback Matthew Stafford during the first half Sunday in Detroit. (AP photo)

ALLEN PARK — Detroit’s much-anticipated defensive front has looked flat so far this season.

This was supposed to be a strength for the Lions, who added defensive linemen Trey Flowers and Mike Daniels in the offseason and traded for Damon Harrison last year. The results have been decidedly mixed, and on Sunday, Detroit struggled to stop the run and rush the passer in a 42-30 loss to Minnesota.

The Lions have played some tough opponents, and their defensive numbers aren’t good: They’ve allowed 429 yards per game, with opponents having success both on the ground and through the air.

“I thought that it was probably closer than where it was yesterday,” coach Matt Patricia said Monday. “I thought yesterday was not where it has been in the past. I think I definitely saw that on tape. That’s why I wanted to go back today and make sure that I was teaching it again, to make sure that I didn’t leave anything out from that aspect through the course of this week that caused us not to play up to some of the technique that we had been doing at this point.”

The Lions have faced a tough slate of quarterbacks so far. Their last five games have been against Phillip Rivers, Carson Wentz, Patrick Mahomes, Aaron Rodgers and Kirk Cousins. Their losses to Kansas City and Green Bay were close, but there were few silver linings at home against the Vikings.

Even amid the excitement of a revamped defensive line, the Lions were dealing with injuries as early as training camp, when Flowers and Harrison missed time. That may have contributed to some of the team’s problems.

“That is one of the things I talk about all the time, how important training camp is — those reps in training camp. The cumulative amount of reps that we get in camp far outweigh the Wednesdays or every other Wednesday kind of repetition that we get,” Patricia said. “It makes it really difficult to catch up and unfortunately, we have to do it every single way we can possible.”

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WHAT’S WORKING

With the exception of a puzzling fourth-down play in the fourth quarter, the offense seemed sharp against the Vikings. Matthew Stafford threw for 364 yards and four touchdowns, and the team’s only turnover came late, when the Lions were rushing to try to make up a 12-point deficit.

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WHAT NEEDS HELP

The defensive line has fallen short of expectations, but the whole defense has room for improvement. Minnesota punted only twice Sunday and had 32 first downs.